The Popular Science Monthly Volume LXXXVI July to September, 1915 The Scientific Monthly Volume I October to December, 1915

Part 6 out of 8

Acting Assistant Surgeon James Carroll, U. S. Army;
Acting Assistant Surgeon Aristides Agramonte, U. S. Army;
Acting Assistant Surgeon Jesse W. Lazear, U. S. Army.

The board will act under general instructions to be
communicated to Major Reed by the Surgeon General of the Army.
Adjutant General

It may be of interest to the reader to learn who these men were
and the reasons why they were probably selected for the work.

Major Reed, the first member in the order of appointment, was
the ranking officer and therefore the chairman of the board. He
was a regular army officer, at the time curator of the Army
Medical Museum in Washington and a bacteriologist of some
repute. He deservedly enjoyed the full confidence of the
surgeon general, besides his personal friendship and regard.
Reed was a man of charming personality, honest and above board.
Every one who knew him loved him and confided in him. A
polished gentleman and a scientist of the highest order, he was
peculiarly fitted for the work before him.

Dr. James Carroll, the second member of the board, was a
self-made man, having risen from the ranks through his own
efforts: while a member of the Army Hospital Corps he studied
medicine and subsequently took several courses at Johns Hopkins
University in the laboratory branches. At the time of his
appointment to the board he had been for several years an able
assistant to Major Reed. Personally, Carroll was industrious
and of a retiring disposition.

Dr. Jesse W. Lazear was the fourth member of the board. He had
graduated from the College of Physicians and Surgeons (Columbia
University) in the same class as the writer, in 1892, and had
afterwards studied abroad and at Johns Hopkins. Lazear had
received special training in the investigation of mosquitoes
with reference to malaria and other diseases. Stationed at
Columbia Barracks, he had been in Cuba several months before
the board was convened, in charge of the hospital laboratory at
the camp. A thorough university man, he was the type of the old
southern gentleman, kind, affectionate, dignified, with a high
sense of honor, a staunch friend and a faithful soldier.

The writer was the third member of the Army Board. Born in Cuba
during the ten years' war, while still a child, my father
having been killed in battle against the Spanish, I was taken
to the United States and educated in the public schools and in
the College of the City of New York, graduating from the
College of Physicians and Surgeons in 1892. At the breaking out
of the war I was assistant bacteriologist in the New York
Health Department. The subject of yellow fever research was my
chief object from the outset, and, at the time the board was
appointed, I was in charge of the laboratory of the Division of
Cuba, in Havana.

It may be readily seen from the brief sketch regarding the
several members that the components of the yellow-fever board
really constituted a perfectly consistent body, for the reason,
mainly, that they were all men trained in the special field
wherein their labors were to be so fruitful and that before
their appointment to the board they had been more or less
associated in scientific work.


My first knowledge of the existence of the board was had
through the following letter from my friend Major Reed:

WASHINGTON, May 25, 1900

Act'g Asst. Surgeon U. S. A.,
Military Hospital No. 1,
Havana, Cuba

My dear Doctor: An order issued yesterday from the War
Department calls for a board of medical officers for the
investigation of acute infectious diseases occurring on the
Island of Cuba. The board consists of Carroll, yourself, Lazear
and the writer. It will be our duty, under verbal instructions
from the Surgeon General, to continue the investigation of the
causation of yellow fever. The Surgeon General expects us to
make use of your laboratory at Military Hospital No. 1 and
Lazear's laboratory at Camp Columbia.

According to the present plan, Carroll and I will be quartered
at Camp Columbia. We propose to bring with us our microscopes
and such other apparatus as may be necessary for the
bacteriological and pathological work. If, therefore, you will
promptly send me a list of the apparatus on hand in your
laboratory, it will serve as a very great help in enabling us
to decide as to what we should include in our equipment. Any
suggestions that you may have to make will be much appreciated.

Carroll and I expect to leave New York, on transport, between
the 15th and 20th of June and are looking forward, with much
pleasure, to our association with you and Lazear in this
interesting work. As far as I can see we have a year or two of
work before us.

Trusting you will let me hear from you promptly, and with best
Sincerely yours,

On the afternoon of June 25, 1900, the four officers met for
the first time in their new capacity, on the veranda of the
officers' quarters at Columbia Barracks Hospital. We were fully
appreciative of the trust and aware of the responsibility
placed upon us and with a feeling akin to reverence heard the
instructions which Major Reed had brought from the surgeon
general; they comprised the investigation also of malaria,
leprosy and unclassified febrile conditions, and were given
with such detail and precision as only a man of General
Sternberg's experience and knowledge in such matters could have
prepared. After deciding upon the first steps to be taken, it
was unanimously agreed that whatever the result of our
investigation should turn out to be, it was to be considered as
the work of the board as a body, and never as the outcome of
any individual effort; that each one of us was to work in
harmony with a general plan, though at liberty to carry out his
individual methods of research. We were to meet whenever
necessary, Drs. Reed, Carroll and Lazear to remain at the
Barracks Hospital and I to stay in charge of the laboratory in
Havana, at the Military Hospital, where I also had a ward into
which yellow-fever cases from the city were often admitted.

Work was begun at once. Fortunately for our purpose, an
epidemic of yellow fever existed in the town of Quemados, in
close proximity to the military reservation of Camp Columbia.
Even before the arrival of Reed and Carroll, Lazear and I had
been studying its spread, following the cases very closely;
subsequently a few autopsies were made by me, Carroll making
cultures from the various tissues and Lazear securing fragments
for microscopical examination; a careful record was kept and
the results noted; cases gradually became less in number as the
epidemic slowly died out, about the middle of August.

In the meantime a rather severe outbreak of yellow fever had
occurred in Santa Clara, a city in the interior of the island,
having invaded the garrison and caused the death of several
soldiers; as the origin of the infection was shrouded in
mystery, and cases continued to appear among the troops even
after they had moved out of the town, it was agreed that I
should endeavor to trace the source of the epidemic and aid the
medical authorities in establishing whatever preventive
measures might seem proper. This service is here recorded
because in the general discussion of the start and course of
the epidemic with Dr. J. Hamilton Stone, the officer in charge
of the military hospital, we incidentally spoke of the possible
agency of insects in spreading the disease, pointing
particularly in this direction the fact of the infection of a
trooper who, suffering from another complaint, occupied a bed
in a ward across the yard from where a yellow fever case had
developed two weeks before.

The infection of the city of Santa Clara had evidently taken
place from Havana, distant only one night's journey by train.
Captain Stone, a particularly able officer, had already
instituted effective quarantine measures before my arrival, so
that I only remained there a few days.

But as to the actual cause of the disease we were still
entirely at sea; it helped us little to know that a man could
be infected in Havana, take the train for a town in the
interior and start an outbreak there in the course of time.

Upon rejoining my colleagues (July 2) we resumed our routine
investigations; not only in Quemados, where the disease was
being stamped out, but also in Havana, at "Las Animas" Hospital
and at Military Hospital No. 1, where my laboratory (the
division laboratory) was located. There was no scarcity of
material and the two members who until then had never seen a
case of yellow fever (Reed and Carroll) had ample opportunity,
and took advantage of it, to become acquainted with the many
details of its clinical picture which escape the ordinary
practitioner, the knowledge and the appreciation of which, in
their relative value, give the right to the title of "expert."

Since the later part of June, reports had been coming to
headquarters of an extraordinary increase of sickness among the
soldiers stationed at Pinar del Rio, the capital of the extreme
western province, and very soon the great mortality from
so-called "pernicious malarial fever" attracted the attention
of the chief surgeon, Captain A. N. Stark, who, after
consulting with Major Reed, ordered me to go there and
investigate. A man had died, supposedly from malaria, just
before my arrival on the afternoon of July 19. The autopsy
which I performed at once showed me that yellow fever had been
the cause of his death, and a search through the military
hospital wards revealed the existence of several unrecognized
cases being treated as malaria; a consultation held with the
medical officer in charge showed me his absolute incapacity, as
he was under the influence of opium most of the time (he
committed suicide several months afterwards), and so I
telegraphed the condition of things to headquarters; in answer
I received the following:

QUEMADOS, CUBA, July 20, 1900

Pinar del Rio Barracks,
Pinar del Rio, Cuba

Report received last night. My thanks are due for your prompt
action and confirmation of my suspicions.
Chief Surgeon

Conditions in the hospital were such as to demand immediate
action; the commander of the post refused to believe he had
yellow fever among his 900 men and was loath to abandon his
comfortable quarters for the tent life in the woods that I
earnestly recommended. In answer to my telegram asking for
official support, I received the following:

QUEMADOS, CUBA, July 21, 1900

Pillar del Rio Barracks,
Pinar del Rio, Cuba

Take charge of cases. Reed goes on morning train. Wire for
anything wanted. Nurses will be sent. Instructions wired
commanding officer. Other doctors should not attend cases.
Establish strict quarantine at hospital. You will be relieved
as soon as an immune can be sent to replace you. Report daily
by wire. STARK,
Chief Surgeon

When Major Reed came to Pinar del Rio (July 21) I had, the day
before, established a separate yellow-fever hospital, under
tents, attended by some of the men who had already passed an
attack and were thus immune. The Major and I went over the
ground very carefully, we studied the sick report for two
months back, fruitlessly trying to place the blame upon the
first case. I well remember how, as we stood in the men's
sleeping quarters, surrounded by a hundred beds, from several
of which fatal cases had been removed, we were struck by the
fact that the later occupants had not developed the disease. In
connection with this, and particularly interesting, was the
case of a soldier prisoner who had been confined to the
guard-house since June 6; he showed the first symptoms of
yellow fever on the twelfth and died on the eighteenth; none of
the other eight prisoners in the same cell caught the
infection, though one of them continued to sleep in the same
bunk previously occupied by his dead comrade. More than this;
the three men who handled the clothing and washed the linen of
those who had died during the last month were still in perfect
health. Here we seemed to be in the presence of the same
phenomenon remarked by Captain Stone in reference to his case
at Santa Clara, and before that by several investigators of
yellow fever epidemics; the infection at a distance, the
harmless condition of bedding and clothing of the sick; the
possibility that some insect might be concerned in spreading
the disease deeply impressed us and Major Reed mentions the
circumstance in his later writings. This was really the first
time that the mosquito transmission theory was seriously
considered by members of the board, and it was decided that,
although discredited by the repeated failure of its most ardent
supporter, Dr. Carlos J. Finlay, of Havana, to demonstrate it,
the matter should be taken up by the board and thoroughly

The removal of the troops out of Pinar del Rio was the means of
at once checking the propagation of the disease.

On the first day of August the board met and after due
deliberation determined to investigate mosquitoes in connection
with the spread of yellow fever. As Dr. Lazear was the only one
of us who had had any experience in mosquito work, Major Reed
thought proper that he should take charge of this part of the
investigation in the beginning, while we, Carroll and I,
continued with the other work on hand, at the same time
gradually becoming familiar with the manipulations necessary in
dealing with the insects.

A visit was now made to Dr. Finlay, who, much elated at the
news that the board was about to investigate his pet theory,
the transmission of yellow fever from man to man by mosquitoes,
very kindly explained to us many points regarding the life of
the one kind he thought most guilty and ended by furnishing us
with a number of eggs which, laid by a female mosquito nearly a
month before, had remained unhatched on the inside of a half
empty bowl of water in his library.

Much to our disappointment and regret, during the first week of
August, Major Reed was recalled to Washington that he might, in
collaboration with Drs. Vaughan and Shakespeare, complete the
report upon "Typhoid Fever in the Army." Thus we were deprived
of his able counsel during the first part of the mosquito
research. Major Reed was detained longer than he expected and
could not return to Cuba until early in October, several days
after Lazear's death.

The mosquito eggs obtained from Dr. Finlay hatched out in due
time; the insects sent to Washington for their exact
classification were declared by Dr. L. O. Howard, entomologist
to the Agricultural Department, to be Culex fasciatus. Later,
they have been called Stegomyia fasciatus and now go under the
name of Stegomyia calopus (Aedes cal.).

Lazear applied some of these mosquitoes to cases of yellow
fever at "Las Animas" Hospital, keeping them in separate glass
tubes properly labeled, and every thing connected with their
bitings was carefully recorded; the original batch soon died
and the work was carried on with subsequent generations from
the same.

The lack of material at Quemados caused us to remove our field
of action to Havana, where cases of yellow fever continued to
appear. We met almost every day at "Las Animas" Hospital, where
Lazear was trying to infect his mosquitoes, or now and then I
performed autopsy upon a case, and Carroll secured sufficient
cultures to last him for several days of bacteriological

Considering that, in case our surmise as to the insect's action
should prove to be correct, it was dangerous to introduce
infected mosquitoes amongst a population of 1,400 non-immunes
at Camp Columbia, Dr. Lazear thought best to keep his
presumably infected insects in my laboratory at the Military
Hospital No. 1, from where he carried them back and forth to
the patients who were periodically bitten.

Incidentally, after the mosquitoes fed upon the yellow fever
patients, they were applied, at intervals of two or three days,
to whoever would consent to run the risk of contracting yellow
fever in this way; needless to say, current opinion was against
this probability and as time passed and numerous individuals
who had been bitten by insects which had previously fed upon
yellow fever blood remained unaffected, I must confess that
even the members of the board, who were rather sanguine in
their expectations, became somewhat discouraged and their faith
in success very much shaken.

No secret was made of our attempts to infect mosquitoes; in
fact many local physicians became intensely interested, and
Lazear and his tubes were the subject of much comment on the
part of the Havana doctors, who nearly twenty years before had
watched and laughed at Dr. Finlay, then bent apparently upon
the same quest in which we were now engaged. Dr. Finlay himself
was somewhat chagrined when he learned of our failure to infect
any one with mosquitoes, but, like a true believer, was
inclined to attribute this negative result more to some defect
in our technique than to any flaw in his favorite theory.

Although the board had thought proper to run the same risks, if
any, as those who willingly and knowingly subjected themselves
to the bites of the supposedly infected insects, opportunity
did not offer itself readily, since Major Reed was away in
Washington and Carroll, at Camp Columbia, engrossed in his
bacteriological investigations came to Havana only when an
autopsy was on hand or a particularly interesting case came up
for study. I was considered an immune, a fact that I would not
like to have tested, for though born in the island of Cuba, I
had practically lived all my life away from a yellow fever
zone; it was therefore presumed that I ran no risk in allowing
mosquitoes to bite me, as I frequently did, just to feed them
blood, whether they had previously sucked from yellow fever
cases or not. And so, time passed and several Americans and
Spaniards had subjected themselves in a sporting mood to be
bitten by the infected (?) mosquitoes without causing any
untoward results, when Lazear applied to himself (August 16,
1900) a mosquito which ten days before had fed upon a mild case
of yellow fever in the fifth day of his disease; the fact that
no infection resulted, for Lazear continued in excellent health
for a space of time far beyond the usual period of incubation,
served to discredit the mosquito theory in the opinion of the
investigators to a degree almost beyond redemption, and the
most enthusiastic, Dr. Lazear himself, was almost ready to
"throw up the sponge."

I had as laboratory attendant a young American, a private
belonging to the Hospital Corps of the Army, who more than once
had bared his arm to allow a weak mosquito a fair meal with
which to regain its apparently waning strength; Loud, for that
was his name, derided the idea that such a little beast could
do so much harm as we seemed ready to accuse it of, although he
was familiar with the destruction caused by bacteria, but then,
he used to say, "bacterial work in armies of more than a
million bugs at the same time and no one would be d---- fool
enough to let more than one or two gnats sting him at once."

This state of things, the gradual loss of faith in the danger
which mosquitoes seemed to possess, led Dr. Lazear to relax a
little and become less scrupulous in his care of the insects,
and often, after applying them to patients, if pressed for
time, he would take them away with him to his laboratory at
Columbia Barracks, where, the season being then quite warm,
they could be kept as comfortably as at the Military Hospital
laboratory. Thus it happened that on the twenty-seventh of
August he had spent the whole morning at "Las Animas" Hospital
getting his mosquitoes to take yellow-fever blood: the
procedure was very simple; each insect was contained in a glass
tube covered by a wad of cotton, the same as is done with
bacterial cultures. As the mouth of the tube is turned
downwards, the insect usually flies towards the bottom of the
tube (upwards), then the latter is uncovered rapidly and the
open mouth placed upon the forearm or the abdomen of the
patient; after a few moments the mosquito drops upon the skin
and if hungry will immediately start operations; when full, by
gently shaking the tube, the insect is made to fly upwards
again and the cotton plug replaced without difficulty. It so
happened that this rather tedious work, on the day above
mentioned, lasted until nearly the noon hour, so that Lazear,
instead of leaving the tubes at the Military Hospital, took
them all with him to Camp Columbia: among them was one insect
that for some reason or other had failed to take blood when
offered to it at "Las Animas" Hospital.

This mosquito had been hatched in the laboratory and in due
time fed upon yellow-fever blood from a severe case on August
15, that is, twelve days before, the patient then being in the
second day of his illness; also at three other times, six days,
four days and two days before. Of course, at the time, no
particular attention had been drawn to this insect, except that
it refused to suck blood when tempted that morning.

After luncheon that day, as Carroll and Lazear were in the
laboratory attending to their respective work, the conversation
turning upon the mosquitoes and their apparent harmlessness,
Lazear remarked how one of them had failed to take blood, at
which Carroll thought that he might try to feed it, as
otherwise it was liable to die before next day (the insect
seemed weak and tired); the tube was carefully held first by
Lazear and then by Carroll himself, for a considerable length
of time, upon his forearm, before the mosquito decided to
introduce its proboscis.

This insect was again fed from a yellow fever case at "Las
Animas" Hospital on the twenty-ninth, two days later, Dr.
Carroll being present, though not feeling very well, as it was
afterwards ascertained.

We three left the yellow-fever hospital together that
afternoon; I got down from the doherty-wagon where the road
forks, going on to the Military Hospital, while Carroll and
Lazear continued on their way to Camp Columbia. On the
following day, Lazear telephoned to me in the evening, to say
that Carroll was down with a chill after a sea bath taken at
the beach, a mile and a half from Camp, and that they suspected
he had malaria; we therefore made an appointment to examine his
blood together the following morning.

When I reached Camp Columbia I found that Carroll had been
examining his own blood early that morning, not finding any
malarial parasites; he told me he thought he had "caught cold"
at the beach: his suffused face, blood-shot eyes and general
appearance, in spite of his efforts at gaiety and unconcern,
shocked me beyond words. The possibility of his having yellow
fever did not occur to him just then; when it did, two days
later, he declared he must have caught it at my autopsy room in
the Military Hospital, or at "Las Animas" Hospital, where he
had been two days before taking sick. Although we insisted that
he should go to bed in his quarters, we could only get him to
rest upon a lounge, until the afternoon, when he felt too sick
and had to take to his bed.

Lazear and I were almost panic-stricken when we realized that
Carroll had yellow fever. We searched for all possibilities
that might throw the blame for his infection upon any other
source than the mosquito which bit him four days before;
Lazear, poor fellow, in his desire to exculpate himself, as he
related to me the details of Carroll's mosquito experiment,
repeatedly mentioned the fact that he himself had been bitten
two weeks before without any effect therefrom and finally, what
seemed to relieve his mind to some extent, was the thought that
Carroll offered himself to feed the mosquito and that he held
the tube upon his own arm until the work was consummated.

I have mentioned before that, as Lazear and I, vaguely hoping
to find malarial parasites in Carroll's blood, sat looking into
our microscopes that morning, the idea that the mosquito was
what brought him down gradually took hold of our minds, but as
our colleague had been exposed to infection in other ways, by
visiting the yellow fever hospital "Las Animas," as well as the
infected city of Havana, it was necessary to subject that same
mosquito to another test and hence the inoculation of Private
Dean, which is described in the opening chapter of this



The month of September, 1900, was fraught with worry and
anxiety: what with Carroll's and Private Dean's attacks of
yellow fever and Major Reed's inability to return, Lazear and I
were well-nigh on the verge of distraction. Private Dean was
not married, but Carroll's wife and children, a thousand miles
away, awaited in the greatest anguish the daily cablegram which
told them the condition of the husband and father, who was
fighting for life, sometimes the victim of the wildest delirium
caused by consuming fever, at others almost about to collapse,
until one day, the worst of the disease being over, the wires
must have thrilled at our announcement, "Carroll out of

Fortunately both he and Dean made an uninterrupted recovery,
but we were still to undergo the severest trial, a sorrow
compared to which the fearful days of Carroll's sickness lose
all importance and dwindle almost into insignificance.

On the morning of the eighteenth my friend and classmate
Lazear, whom in spite of our short intercourse I had learned to
respect and in every way appreciate most highly, complained
that he was feeling "out of sorts." He remained all day about
the officers' quarters and that night suffered a moderate
chill. I saw him the next day with all the signs of a severe
attack of yellow fever.

Carroll was already walking about, though enfeebled by his late
sickness, and we both plied Lazear with questions as to the
origin of his trouble; I believe we affectionately chided him
for not having taken better care of himself. Lazear assured us
that he had not experimented upon himself, that is, that he had
not been bitten by any of the purposely infected mosquitoes.

After the case of Dean so plainly demonstrated the certainty of
mosquito infection, we had agreed not to tempt fate by trying
any more upon ourselves, and even I determined that no mosquito
should bite me if I could prevent it, since the subject of my
immunity was one that could not be sustained on scientific
grounds; at the same time, we felt that we had been called upon
to accomplish such work as did not justify our taking risks
which then seemed really unnecessary. This we impressed upon
Major Reed when he joined us in October and for this reason he
was never bitten by infected mosquitoes.

Lazear told us, however, that while at "Las Animas" Hospital
the previous Thursday (five days before), as he was holding a
test-tube with a mosquito upon a man's abdomen, some other
insect which was flying about the room rested upon his hand; at
first, he said, he was tempted to frighten it away, but, as it
had settled before he had time to notice it, he decided to let
it fill and then capture it; besides, he did not want to move
in fear of disturbing the insect contained in his tube, which
was feeding voraciously. Before Lazear could prevent it, the
mosquito that bit him on the hand had flown away. He told us in
his lucid moments, that, although Carroll's and Dean's cases
had convinced him of the mosquito's role in transmitting yellow
fever, the fact that no infection had resulted from his own
inoculation the month before had led him to believe himself, to
a certain extent, immune.

How can I describe the agony of suspense which racked our souls
during those six days? It seemed to us as though a life was
being offered in sacrifice for the thousands which it was to
contribute in saving. Across the span of thirteen years the
memory of the last moments comes to me most vividly and
thrilling, when the light of reason left his brain and shut out
of his mind the torturing thought of the loving wife and
daughter far away, and of the unborn child who was to find
itself fatherless on coming to the world.

Tuesday, the twenty-fifth of September saw the end of a life
full of promise; one more name, that of Jesse W. Lazear, was
graven upon the portals of immortality. And we may feel justly
proud for having had it, in any way, associated with our own.

The state of mind in which this calamity left us may better be
imagined than described. The arrival of Major Reed several days
after in a great measure came to relieve the tensity of our
nerves and render us a degree of moral support of which we were
sorely in need.

Lazear's death naturally served to dampen our fruition at the
success of the mosquito experiments, but, this notwithstanding,
when the facts were known we were the subjects of much
congratulation and the question whether the theory had been
definitely demonstrated or not was the theme of conversation
everywhere, about Havana and Camp Columbia particularly. We
fully realized that three cases, two experimental and one
accidental, were not sufficient proof, and that the medical
world was sure to look with doubt upon any opinion based on
such meager evidence; besides, in the case of Carroll, we had
been unable to exclude the possibility of other means of
infection, so that we really had but one case, Dean's, that we
could present as clearly demonstrative and beyond question. In
spite of this, we thought that the results warranted their
presentation in the shape of a "Preliminary Note," and after
all the data were carefully collected from Lazear's records and
those at the Military Hospital, a short paper was prepared
which the Major had the privilege to read at the meeting of the
American Public Health Association, held on October 24, in the
city of Indianapolis.

For this purpose Major Reed went to the States two weeks after
his return to Cuba, and Carroll also took a short leave of
absence so as to fully recuperate, in preparation for the
second series of inoculations which we had arranged to
undertake, after the Indianapolis meeting.

These inoculations, according to our program, were to be made
upon volunteers who should consent to suffer a period of
previous quarantine at some place to be selected in due time,
away from any possibility of yellow fever.

It so happened then that I was left the only member of the
board in Cuba and, under instructions from Major Reed, I began
to breed mosquitoes and infect them, as Lazear used to do,
wherever cases occurred, keeping them at my laboratory in the
Military Hospital No. 1. Major Reed had also asked me to look
about for a proper location wherein to continue the work upon
his return.


The possible agency of insects in the propagation of yellow
fever was thought of by more than one observer, from a very
early period in the history of this disease. For instance,
Rush, of Philadelphia, in 1797, noticed the excessive abundance
of mosquitoes during that awful epidemic. Subsequently, several
others spoke of the coincidence of gnats or mosquitoes and
yellow fever, but without ascribing any direct relation to the
one regarding the other. Of course, man-to-man infection
through the sole intervention of an insect was a thing entirely
inconceivable and therefore unthought of until very recently,
and in truth the discovery, as far as yellow fever is
concerned, was the result of a slow process of evolution of the
fundamental fact, taken in connection with similar findings, in
other diseases.

The earliest direct reference is found in the writings of Dr.
Nott, of Mobile, Ala., who in 1848 suggested that the
dissemination of the yellow fever poison was evidently by means
of some insect "that remained very close to the ground." But
the first who positively pointed to the mosquito as the
spreader of yellow fever, who showed that absence of mosquitoes
precluded the existence of the disease and who prescribed the
ready means to stamp it out, by fumigation and by preventing
the bites of the insects, was Dr. Louis D. Beauperthuy, a
French physician, then located in Venezuela. The writer has an
original copy of his paper, published in 1853, where he fastens
the guilt upon the domestic mosquitoes, believing, in accord
with the prevailing teachings of medical science, that the
mosquitoes infected themselves by contact or feeding upon the
organic matter found in the stagnant waters where they are
hatched, afterwards inoculating the victims by their sting. He
recognized the fact that yellow fever is not contagious and
therefore could not think of the possibility of man-to-man
infection, as we know it to-day. The keenest observer was this
man Beauperthuy, and, even at that benighted time in the
history of tropical medicine, made most interesting studies of
the blood and tissues, employing the microscope and the
chemical reactions in his research. No one believed him, and a
commission appointed to report upon his views said that they
were inadmissible and all but declared him insane.

This field of investigation remained dormant for a
comparatively long period of time. Meanwhile another medical
writer, Dr. Greenville Dowell, mentions in 1876, that "if we
compare the effect of heat and cold on gnats and mosquitoes
with yellow fever, it will be difficult to believe it is of the
same nature, as it is controlled by the same natural laws."
Soon after this, in 1879, the first conclusive proof of the
direct transmission of a disease from man-to-man was presented
by the father of tropical medicine, Sir Patrick Manson, with
regard to filaria, a blood infection that often causes the
repulsive condition known as elephantiasis and which the
mosquito takes from man and after a short time gives over to
another subject. This discovery attracted world-wide attention
and many looked again towards the innumerable species of biting
insects that dwell in the Tropic Zone, as possible carriers of
the obscure diseases which also prevail in those regions.

In 1881, Dr. Carlos Finlay, of Havana, in an exhaustive paper
read before the Royal Academy of Sciences, gave as his opinion
that yellow fever was spread by the bites of mosquitoes
"directly contaminated by stinging a yellow fever patient (or
perhaps by contact with or feeding from his discharge)." This
latter view he held as late as 1900, which, although correct in
the main fact of the transmission of the germ from a patient to
a susceptible person by the mosquito, the modus operandi, as he
conceived it, was entirely erroneous.

Dr. Finlay, unfortunately was unable to produce experimentally
a single case of fever that could withstand the mildest
criticism, so that at the time when the Army Board came to
investigate the causes of yellow fever in Cuba, his theory,
though practically the correct one, had been so much
discredited, in a great measure by his own failures, that the
best-known experts considered it as an ingenious, but wholly
fanciful, one and many thought it a fit subject for humorous
and sarcastic repartee. Finlay also believed, erroneously, that
repeated bites of contaminated insects might protect against
yellow fever and that the mosquitoes were capable of
transmitting the germ to the next generation.

The wonderful discoveries of Theobald Smith, as to the agency
of ticks in spreading Texas fever of cattle, and those of Ross
and the Italian investigators who showed conclusively that
malaria was transmitted by a species of mosquito, brought the
knowledge of these various diseases to the point where the Army
Board took up the investigation of yellow fever.


Major Reed came back to Havana in the early part of November,
Carroll following a week after.

During their absence, I had been applying mosquitoes to yellow
fever patients at "Las Animas" Hospital, keeping them in my
laboratory, as it was done at the beginning of the
investigation; the season being more advanced, now and then a
cold "norther" would blow and my insects suffered very much
thereby, so that I had the greatest trouble in preventing their
untimely death: to this may be added the difficulty met in
feeding them blood, for now that I knew their sting was
dangerous, unto death perhaps, I could not allow any
indiscriminate biting, but had to select for the purpose
individuals who had suffered an attack of the disease and were
therefore immune.

The necessity for an experimental camp became more imperative
as time passed, not only where proper quarantine and isolation
could be established, but also where the insects intended for
the inoculations might receive better care. This entailed
considerable expense.

Fortunately for us, the military governor of the island at that
time, Brigadier General Leonard Wood, was a man who had
received a thorough medical training; broad and clear-minded,
he fully appreciated the importance of what might be the
outcome of our researches. We found in him the moral support
which we so much needed and, further, he promptly placed at the
disposal of the board sufficient funds with which to carry on
the experiments to the end. I firmly believe that had other
been the circumstances, had a more military and less scientific
man been at the head of the government, the investigation would
have terminated there and then, and many years would have
passed, with hundreds of lives uselessly sacrificed, before we
could have attained our present remarkable sanitary triumphs.

We immediately set about choosing a location for our camp. I
had already looked over the ground, preferring the proximity of
Camp Columbia, from where supplies could be easily obtained and
because the Military Hospital there could be used for treating
the cases that we intended to produce; I was therefore
favorably impressed with the seclusion offered by a spot
situated a short distance from the main road, in a farm, named
San Jose, belonging to my friend Dr. Ignacio Rojas, of Havana.
Major Reed decided upon this place after looking at many others
in the neighborhood, so that on the twentieth of November we
inaugurated our camp, which we named Camp Lazear, in honor to
the memory of our dead colleague, consisting then of seven army
tents, guarded by a military garrison, composed of men who had
been carefully selected by virtue of their previous good record
and their interest in the work to be undertaken.

Feeling that we had proved, to ourselves at least, the agency
of the mosquito in yellow fever, it became our duty to disprove
the theory, until then held as a certainty by many authorities,
to the effect that the soiled bedding and clothing, the
secretions and excreta of patients, were infectious and in some
way carried the germ of the disease. We therefore designed a
small wooden building, to be erected a short distance from the
tense, with a capacity of 2,800 cubic feet. The walls and
ceiling were absolutely tight, the windows and vestibuled door
screened and all precautions taken to prevent the entrance of

Into this, called the "infected clothing building," three beds
and a stove, to maintain a high tropical temperature, were
introduced; also mattresses and pillows, underwear, pajamas,
towels, sheets, blankets, etc., soiled with blood and
discharges from yellow fever cases: these articles were put on
the beds, hung about the room and packed in a trunk and two
boxes placed there for the purpose.

The building was finished and equipped on November 30. That
Friday evening, Dr. Robert P. Cook, U. S. Army, with two other
American volunteers, entered it and prepared to pass the night:
they had instructions to unpack the boxes and trunk, to handle
and shake the clothing and in every way to attempt to
disseminate the yellow fever poison, in case it was contained
in the various pieces. We watched the proceedings from the
outside, through one of the windows. The foul conditions which
developed upon opening the trunk were of such a character that
the three men were seen to suddenly rush out of the building
into the fresh air; one of them was so upset that his stomach
rebelled; yet, after a few minutes, with a courage and
determination worthy only of such a cause, they went back into
the building and passed a more or less sleepless night, in the
midst of indescribable filth and overwhelming stench.

For twenty consecutive nights these men went through the same
performance; during the day they remained together, occupying a
tent near their sleeping quarters. Dr. Cook, by voluntarily
undergoing such a test, without remuneration whatsoever, proved
his faith in the mosquito theory; his demonstration of the
harmless character of so-called infected clothing, in yellow
fever, has been of the greatest importance. The other six men
(two of them with Dr. Cook) who were subjected to this test,
received each a donation of one hundred dollars for his

Many days even before the establishment of the experimental
camp, the board had heard that several men who knew of our work
were willing to submit to the inoculations and thus aid in
clearing up the mystery of yellow fever. Two of these require
special mention, John R. Kissinger, a private in the Hospital
Corps of the Army, was the first to offer himself most
altruistically, for, as he expressed it, his offer was made
without any desire for pecuniary or other consideration and
solely "in the interest of humanity and the cause of science,"
the other, J. J. Moran, a civilian employee, also stipulated as
a condition that he was to receive no pay for his services.
Both these men, in due time, suffered from yellow fever and
until very recently had never obtained any reward for the great
risk which they ran so voluntarily and praiseworthily.

Kissinger, who after several years' service in the army became
disabled, is receiving a pension from the government; Moran, I
hope, is still well and in the employ of the Isthmian Canal
Commission, justly enjoying the friendship and confidence of
his superior officers. The names of Kissinger and Moran should
figure upon the roll of honor of the U. S. Army.

On the day the camp was definitely organized, Kissinger, who
had not gone outside the military reservation for more than a
month, moved into Camp Lazear and received his first bite from
a mosquito which evidently was not "loaded" for, again on
November 23, he was stung by the same insect without result. On
December 5, five mosquitoes were applied, which brought about a
moderate infection in three days. Moran was also bitten by
mosquitoes which were supposed to be infected on November 26
and 29, both times unsuccessfully. As will be seen, he was
infected later on.

By this time we had decided, the weather having cooled
considerably, that it was better to keep the mosquitoes at a
higher temperature and nearer to the men who were to be
inoculated; therefore it was planned to put up another small
wooden structure, which was to be known as the "Mosquito
Building" in which an artificial temperature could be
maintained; at my suggestion, the building was so designed that
it might serve to infect individuals; by liberating infected
mosquitoes on the inside and exposing some person to their
stings, we could try to reproduce the infection as we felt it
occurred in nature. Another reason for the mosquito house was
the need to obviate the transportation of the insects from the
Military Hospital, where I kept them, to our camp, which could
not be easily done without subjecting them to severe injury.
Upon one occasion I was taking four infected mosquitoes in the
pocket inside my blouse from the laboratory in Havana to the
experimental camp, accompanied by my attendant Private Loud;
the horse which pulled my buggy, a rather spirited animal,
becoming frightened at a steam roller, as we went around the
corner of Colon Cemetery, started to race down the hill towards
the Almendares River: Loud was thrown out by the first
cavortings of the horse, who stood on its hind legs and jumped
several times before dashing away, while I held tightly to the
tubes in my pocket, as the buggy upset and left me stranded
upon a sand pile in the middle of the road; the mosquitoes were
quite safe, however, and upon my arrival at Camp Lazear I
turned them over to Carroll for his subsequent care.

Another difficulty afterwards encountered was the scarcity of
material susceptible to infection, for, although several men
had expressed a willingness to be inoculated, when the time
came; they all preferred the "infected clothing" experiment to
the stings of our mosquitoes. We then thought best to secure
lately landed Spaniards, to whom the probable outcome of the
test might be explained and their consent obtained for a
monetary consideration. Our method was as follows; as soon as a
load of immigrants arrived, I would go to Tiscornia, the
Immigration Station across the Bay of Havana, and hire eight or
ten men, as day laborers, to work in our camp. Once brought in,
they were bountifully fed, housed under tents, slept under
mosquito-bars and their only work was to pick up loose stones
from the grounds, during eight hours of the day, with plenty of
rest between. In the meantime, as the days of observation
passed, I carefully questioned them as to their antecedents,
family history and the diseases which they might have suffered;
those who had lived in Cuba or any other tropical country
before were discarded at once and also those who were under age
or had a family dependent upon them. When the selection was
finally made, the matter of the experiment was put to them.
Naturally, they all felt more or less that they were running
the risk of getting yellow fever when they came to Cuba and so
were not at all averse to allow themselves to be bitten by
mosquitoes: they were paid one hundred dollars for this, and
another equal sum if, as a result of the biting experiment,
they developed yellow fever. Needless to say, no reference was
made to any possible funeral expenses. A written consent was
obtained from each one, so that our moral responsibility was to
a certain extent lessened. Of course, only the healthiest
specimens were experimented upon.

It so happened that some reporter discovered what we were
about, or perhaps some invidious person misrepresented the
facts; at any rate, on the twenty-first of November a Spanish
newspaper appeared with flaring headlines denouncing the
American doctors who were taking advantage of the poor
immigrants and experimenting with them by injecting all sorts
of poisons! It called upon the Spanish consul to look after his
subjects. In view of this we felt that if such campaign
continued, in a short time it would either make it impossible
to secure subjects or cause diplomatic pressure to be exerted
against the continuance of our experiments. It was thought best
to "beard the lion in his den" so the three of us called upon
the consul the following day. He was surprised to hear one of
us address him in his own language, having taken us all for
Americans on first sight, and when I explained to him our
method of procedure and showed him the signed contracts with
the men, being an intelligent man himself, he had no objections
to offer and told us to go ahead and not bother about any howl
the papers might make.

The first three cases (two of them Spaniards) which we produced
came down with yellow fever within a very short period, from
December 8 to 13; it will therefore not surprise the reader to
know that when the fourth case developed on December 15, and
was carried out of the camp to the hospital, it caused a
veritable panic among the remaining Spaniards, who, renouncing
the five hundred pesetas that each had in view, as Major Reed
very aptly put it, "lost all interest in the progress of
science and incontinentally severed their connection with Camp

But there was a rich source to draw from, and the unexpected
stampede only retarded our work for a short time. Our
artificial epidemic of yellow fever was temporarily suspended
while a new batch of susceptible material was brought in,
observed and selected. The next case for that reason was not
produced upon a Spaniard until December 30.

In the face of the negative experiments with supposedly
contaminated articles, it rested with us to show how a house
became infected and for this purpose the main part of the
"mosquito building" was utilized.

This chamber was divided into two compartments by a double
wire-screen partition, which effectually prevented mosquitoes
on one side from passing to the other; of course there were no
mosquitoes there to begin with, as the section of the building
used for breeding and keeping them was entirely separated from
the other, and there could be no communication between them.

On the morning of December 21, a jar containing fifteen hungry
mosquitoes, that had previously stung cases of yellow fever,
was introduced and uncovered in the larger compartment, where a
bed, with all linen perfectly sterilized, was ready for
occupancy. A few minutes after, Mr. Moran, dressed as though
about to retire for the night, entered the room and threw
himself upon the bed for half an hour; during this time two
other men and Major Reed remained in the other compartment,
separated from Moran only by the wire-screen partition. Seven
mosquitoes were soon at work upon the young man's arms and
face; he then came out, but returned in the afternoon, when
five other insects bit him in less than twenty minutes. The
next day, at the same hour of the afternoon, Moran entered the
"mosquito building" for the third time and remained on the bed
for fifteen minutes, allowing three mosquitoes to bite his
hands. The room was then securely locked, but the two Americans
continued to sleep in the other compartment for nearly three
weeks, without experiencing any ill effects.

Promptly on Christmas morning Moran, who had not been exposed
to infection except for his entrance into the "mosquito
building" as described, came down with a well-marked attack of
yellow fever.

The temperature in this room, where these mosquitoes had been
released, was kept rather high and a vessel with water was
provided, where they might lay their eggs if so inclined, but
notwithstanding all these precautions, it was subsequently
found that the insects had been attacked by ants, so that by
the end of the month only one of the fifteen mosquitoes
remained alive.

It is hardly necessary to detail here how seven other men were
subjected to the sting of our infected mosquitoes, of which
number five developed the disease, but it may be interesting to
note that two of these men had been previously exposed in the
"infected clothing building" without their becoming infected,
showing that they were susceptible to yellow fever after all.

The evidence so far seemed to show that the mosquito could only
be infected by sucking blood of a yellow-fever patient during
the first three days of the disease; to prove that the parasite
was present in the circulating blood at that time we therefore
injected some of this fluid taken from a different case each
time, under the skin of five men: four of these suffered an
attack of yellow fever as the result of the injection. The
other one, a Spaniard, could not be infected either by the
injection of blood or the application of mosquitoes which were
known to be infected, showing that he had a natural immunity
or, more likely, that he had had yellow fever at some previous

While selecting the Spaniards, it was often ascertained that
they had been in Cuba before, as soldiers in the Spanish army
usually, and the natural conclusion was that they had undergone
infection; it was very seldom that any escaped during the
Spanish control of the island.

Thus terminated our experiments with mosquitoes which, though
necessarily performed on human beings, fortunately did not
cause a single death; on the other hand, they served to
revolutionize all standard methods of sanitation with regard to
yellow fever. They showed the uselessness of disinfection of
clothing and how easily an epidemic can be stamped out in a
community by simply protecting the sick from the sting of the
mosquitoes and by the extensive and wholesale destruction of
these insects which, added to the suppression of their breeding
places, if thoroughly carried out, are the only measures
necessary to forever rid a country of this scourge.

Besides keeping a sharp lookout against the importation of
yellow fever cases, these are the simple rules that have kept
the Panama Canal free and prevented the slaughter of hundreds
of foreigners, so generally expected every year, in former

Since we made our demonstration in 1901, our work has been
corroborated by various commissions appointed for the purpose,
in Mexico, Brazil and Cuba, composed variously of Americans,
French, English, Cuban, Brazilian and German investigators.
Nothing has been added to our original findings; nothing has
been contradicted of what we have reported, and to-day, after
nearly thirteen years, the truths that we uncovered stand
incontrovertible; besides, they have been the means of driving
out yellow fever from Cuba, the United States (Laredo, Texas,
1903 and New Orleans, La., 1905), British Honduras and several
cities of Brazil.

Of the Army Board only I remain. Lazear, as reported, died
during the early part of our investigations; Reed left us in
1902 and Carroll only five years later. The reader may wonder
of what benefit was it to us, this painstaking and remarkable
accomplishment which has been such a blessing to humanity! See
what the late Surgeon General of the U. S. Army had to say in
his report (Senate Document No. 520, Sixty-first Congress,
second session):

1. Major Walter Reed, surgeon, United States Army, died in
Washington, D. C., from appendicitis, November 23, 1902, aged
51. His widow, Emilie Lawrence Reed, is receiving a pension of
$125 a month.

2 Maj. James Carroll was promoted from first lieutenant to
major by special act of Congress, March 9, 1907. He died in
Washington, D C., of myocarditis, September 16, 1907. His
widow, Jennie H. Carroll, since his death, has received an
annuity of $125 a month, appropriated from year to year in the
Army appropriation bill.

3. Dr. Jesse W. Lazear, contract surgeon, United States Army,
died at Camp Columbia, Cuba, of yellow fever, September 25,
1900. His widow, Mabel M. Lazear, since his death, has received
an annuity of $125 a month appropriated from year to year in
the Army appropriation bill.

4. Dr. Aristides Agramonte is the only living member of the
board. He is professor of bacteriology and experimental
pathology in the University of Habana and has never received,
either directly or indirectly, any material reward for his
share in the work of the board.

It is not for me to make any comments: the above paragraphs
have all the force of a plain, truthful statement of facts.
Perhaps it is thought that enough reward is to be found in the
contemplation of so much good derived from one's own efforts
and the feeling it may produce of innermost satisfaction and in
forming the belief that one had not lived in vain. In a very
great measure, I know, the thought is true.





THE most elaborate structure yet proposed to explain the origin
of the solar system is the planetesimal hypothesis by
Chamberlin and Moulton. The energy which these investigators
have devoted to formulating and testing this hypothesis, in the
light of the principles of mechanics, has been commensurate
with the importance of the subject. They postulate that the
materials now composing the Sun, planets, and satellites, at
one time existed as a spiral nebula, or as a great spiral swarm
of discrete particles, each particle in elliptic motion about
the central nucleus. The authors go further back and endeavor
to account for the origin of the spiral nebula, but this phase
of the subject is not vital to their hypothesis. However, it
conduces to clearness in presenting their hypothesis to begin
with the earlier process.

It may happen, once in a while, that two stars will collide. If
the collision is a grazing one, they say, a spiral nebula will
be formed. However, a fairly close approach of two stars will
occur in vastly greater frequency and the effect of this
approach will also be to form a spiral nebula or two such
nebulae. The authors recall that our Sun is constantly ejecting
materials to a considerable height to form the prominences, and
that the attractions of a great star passing fairly close to
our solar system would assist this process of expulsion of
matter from the Sun. A great outbreak or ejection of matter
would occur not only on the side of our Sun turned toward the
disturbing body, but on the opposite side as well, for the same
reason that tides in our oceans are raised on the side opposite
the Moon as well as on the side toward the Moon. As the Sun and
disturbing star proceeded in their orbits, the stream of matter
leaving our Sun on the side of the disturbing body would try to
follow the other star; and the stream of matter leaving the
other side of the Sun would shoot out in curves essentially
symmetrical with those in the first stream. As the disturbing
star approached and receded the paths taken by the ejected
matter would be successively along curves such as are
represented by the dotted lines in Fig. 28. At any given moment
the ejected matter would lie on the two heavy lines. The matter
would not be moving along the heavy lines, but nearly at right
angles to them, in the directions that the lighter curves are
pointing. As the ejections would not be continuous, but on the
contrary intermittent, because of violent pulsations of the
Sun's body, there would be irregularities in the two spiral
streamers. The materials drawn out of the Sun would revolve
around it in elliptic orbits after the disturbing body had
passed beyond the distance of effective disturbance, as
illustrated in Fig. 29. The orbits of the different masses
would have different sizes and different eccentricities. There
would also be a wide distribution of finely-divided material
between the main branches of the spiral. All of the widespread
gaseous matter, hot when it left the Sun, would soon become
cold, by expansion and radiation; and only the massive nuclei
would remain gaseous and hot.

I see no reason to question the efficiency of this ingenious
explanation of the origin of a spiral nebula: the close passage
of two massive stars could, in my opinion, produce an effect
resembling a spiral nebula, quite in accordance with Moulton's
test calculations upon the subject. Some of the spirals have
possibly been formed in this way (see Fig. 30); but that the
tens of thousands of spirals known to exist in the sky have
actually been produced in this manner is another question, and
one which, in my opinion, is open to grave doubt. But to this
point we shall return later.

There are marked advantages in starting the evolution of the
solar system from a spiral nebula, aside from the fact that
spirals are abundant, and therefore represent a standard
product of development. The material is thinly and very
irregularly distributed in a plane passing through the Sun, and
the motions around the Sun are all in the same direction. The
great difficulty in the Laplace hypothesis, as to the constancy
of the moment of momentum, is here eliminated. There are
well-defined condensations of nuclei at quite different
distances from the Sun. According to this hypothesis the
principal nuclei are the beginnings of the future planets. They
draw into themselves the materials with which they come in
contact by virtue of the crossings of the orbits of various
sizes and various eccentricities. The growth of the planets is
gradual, for the sweeping up and combining process must be
excessively slow. The satellites are started from those smaller
nuclei which happen to be moving with just the right speeds not
to escape entirely the attractions of the principal nuclei, nor
to fall into them. The planes of the planetary orbits and, in
general, the planes of the satellite orbits should agree quite
closely with each other, but they could differ and should
differ from that of the Sun's equator.

The authors call attention to the fact that the Sun's equator
is inclined at a small angle, 7 degrees, to the common planes
of the planetary system, and Chamberlin holds this to be one of
the strong points in favor of the planetesimal hypothesis. He
reasons thus: the star which passed close to our Sun and drew
out the planetary materials in the form of spiral streams must
have moved in the plane of the spiral; that is, in the plane of
our planetary system. Some of the materials would be drawn out
from our Sun only a very short distance and then fall back upon
the Sun. Great tidal waves would be formed on opposite sides of
the Sun, and these would try to follow the disturbing body. The
effect of these waves and of the materials which fall back
would be to change the Sun's original rotation plane in the
direction of the disturbing body's orbital plane.

Now the chance for a disturbing star's passing around our Sun
in a plane making a large angle, say from 45 degrees to 90
degrees, with the Sun's equator, is much greater than for a
small angle 0 degrees to 45 degrees. The chances are greatest
that the angle will be 90 degrees. Only those disturbing stars
which approach our Sun PRECISELY in the plane of the Sun's
equator could move around the Sun in this plane. All those
approaching along any line parallel to the Sun's equatorial
plane, but lying outside of this plane, and all those whose
directions of approach make any angle whatever with the
equatorial plane, would find it impossible to move in that
plane. That the angle under this hypothesis is only 7 degrees
is surprising, though, as we are dealing with but a single
case, we can not say, I think, that this militates either for
or against the hypothesis. We are entitled to say only that
unless the approach was so close as to cause disturbances in
our Sun to relatively great depths, the angle referred to would
have only one chance in ten or fifteen or twenty to be as small
as 7 degrees. Any disturbance which succeeded in taking out of
the Sun only 1/7 of 1 per cent. of its mass could scarcely
succeed in shifting the axis of rotation of the remaining 99
6/7 per cent. very much, I think. If the angle were 30 degrees
or 50 degrees or 80 degrees, instead of 7 degrees, the case for
the planetesimal hypothesis would be somewhat stronger.

A remarkable fact concerning the Sun is that the equatorial
region rotates once around in a shorter time than the regions
in higher latitudes require. The rotation period of the Sun's
equator is about 24 days; the period at latitude 45 degrees is
28 days; and at 75 degrees, 33 days. The planetesimal
hypothesis attributes this equatorial acceleration to the
falling back into the Sun of the materials which had been
lifted out to a short distance by the disturbing body, and to
the forward-rushing tide raised in the equatorial regions by
the disturbing body. This may well have occurred. However, we
must remember that the same phenomenon exists certainly in
Jupiter and Saturn, and quite probably in Uranus and Neptune;
that is, in all the bodies in the system that are gaseous and
free to show the effect. It seems to be the result of a
principle which has operated throughout the solar system, not
requiring, at least not directly requiring, the passage of a
disturbing star. I think the most plausible explanation of this
curious phenomenon is that great quantities of materials
originally revolving around the Sun and around each of the
planets have gradually been drawn into these bodies, by
preference into their equatorial areas. Such masses of matter
moving in orbits very close to these bodies must have traveled
with speeds vastly higher than the surface speeds of the
bodies. To illustrate, the rotational velocity of a particle
now in the Sun's surface at the equator is approximately 2 km.
per second. A small body revolving around the Sun close to his
surface, rapidly enough to prevent its falling quickly upon the
Sun, must have a velocity of more than 400 km. per second. If,
now, this small body encounters some resistance it will fall
into the Sun, and as it is traveling more than 200 times as
rapidly as the solar materials into which it drops, it will
both generate heat and accelerate the rotational velocity of
the surrounding materials. In the same way the equatorial
accelerations in Jupiter and Saturn can receive simple
explanation. The point is not necessarily in opposition to the
planetesimal hypothesis; but whatever the explanation, it ought
to apply to the planet as well as to the Sun.

If the spiral nebulae have been formed in accordance with
Chamberlin and Moulton's hypothesis, the secondary nuclei in
them must revolve in a great variety of elliptic orbits. The
orbits would intersect, and in the course of long ages the
separate masses would collide and combine and the number of
separate masses would constantly grow smaller. Moulton has
shown that IN GENERAL the combining of two masses whose orbits
intersect causes the combined mass to move in an orbit more
nearly circular than the average orbit of the separate masses,
and in general in orbit planes more nearly coincident with the
general plane of the system. Accordingly, the major planets
should move in orbits more nearly circular and more nearly in
the plane of the system than do the asteroids; and so they do.
If the asteroids should combine to form one planet the orbit of
this planet should be much less eccentric than the average of
all the present asteroid eccentricities, and the deviation of
its orbit plane should be less than the average deviation of
the present planes. We can not doubt that this would be the
case. Mercury and Mars, the smallest planets, should have,
according to this principle, the largest eccentricities and
orbital inclinations of any of the major planets. This is true
of the eccentricities, but Mars's orbit plane, contrarily, has
a small inclination. Venus and the Earth, next in size, should
have the next largest inclinations and eccentricities, but they
do not; Venus's eccentricity is the smallest of all. The
Earth's orbital inclination and eccentricity are both small.
Jupiter and Saturn, Uranus and Neptune, should have the
smallest orbital inclinations; their average inclination is
about the same as for Venus and the Earth. They should likewise
have the smallest eccentricities. Neptune, the smallest of the
four, has an orbit nearly circular; Jupiter, Saturn and Uranus
have eccentricities more than 4 times those of Venus and the
Earth. Considering the four large planets as one group and the
four small planets as another group, we find that the
inclinations of the orbits of the two groups, per unit mass,
are about equal; but the average eccentricity of the orbits of
the large planets, per unit mass, is 21 times that of the
orbits of the small planets.[1] The evidence, except as to the
asteroids and Mercury, is not favorable to the planetesimal
hypothesis, unless we make special assumptions as to the
distribution of materials in the spiral nebulae.

[2] The average eccentricity of the orbits of the four inner
planets (per unit mass) is 0.0221, and of the four outer
planets is 0.0489.

The fact that the disturbing body drew 225 times as much matter
a great distance to form the four large planets as it drew out
a short distance to form the four small planets and the
asteroids seems difficult of explanation on the planetesimal
hypothesis. However, this distribution of matter is at present
a difficulty in any of the hypotheses. The planetesimal
hypothesis explains well all west to east rotations of the
planets on their axes, but to make Uranus rotate nearly at
right angles to the plane of the system, and Neptune in a plane
inclined 135 degrees to the plane of the system, is a
difficulty in any of the hypotheses, unless special assumptions
are made to fit each case.

The authors succeed well, I think, in showing that the
satellites should prefer to revolve around their planets in the
direction of the planetary revolution and rotation, especially
for close satellites, and, on the basis of special assumptions,
in the reverse direction for satellites at a greater distance.
They show that the chances favor small eccentricities for
satellites revolving about their planets in the west to east,
or direct sense, and large eccentricities for satellites moving
in retrograde directions. The inner satellite of Mars and the
rings of Saturn make no special difficulty under the
planetesimal hypothesis.

The evidence of the comets, as bona fide members of the solar
system which approach the Sun almost, and perhaps quite,
indifferently from all directions, is that the volume of space
occupied by the parent structure of the system was of enormous
dimensions, both at right angles to the present principal plane
of the system and in that plane. We are accustomed to think of
the spiral nebulae as thin relatively to their major diameters.
To this extent the planetesimal hypothesis does not furnish a
good explanation of the origin of comets, unless we assume that
a small amount of matter was widely scattered in all directions
around the parent spiral; and this conception leads to some
apparent difficulties. The origin of the comets is difficult to
explain under any of the hypotheses.


Kant's hypothesis had the great defect of trying to prove too
much. It started from matter AT REST, and came to grief in
trying to give a motion of rotation to the entire mass through
the operation of internal forces alone--an impossibility.
Kant's idea of nuclei or centers of gravitational attraction,
scattered here and there throughout the chaotic mass, which
grew into the planets and their satellites, is very valuable.

Laplace's hypothesis had the great advantage of starting with
an extended mass already in rotation, but it violated fatally
the law of constancy of moment of momentum. We should expect
this hypothesis to create a solar system free from
irregularities, very much as if it were the product of an
instrument-maker's precision lathe. The solar system as it
exists is a combination of regularities and many surprising

Chamberlin and Moulton's hypothesis has the advantage of a
parent mass in rotation, practically in a common plane, and
with the materials distributed at distances from the nucleus as
nearly in harmony with the known distribution of matter in the
solar system as we care to have them, except perhaps as to the
comets. In effect it retains all the advantageous qualities of
Kant's proposals. It seems to have the flexibility required in
meeting the irregularities that we see in our system.


I think it is very doubtful whether the spiral nebulae have in
general been formed by the close approaches of pairs of stars,
as the authors have postulated for the assumed solar spiral.[2]
The distribution of the spirals seems to me to negative the
idea. To witness the close approach of two stars we must look
in the direction where the stars are. To the best of
present-day knowledge the stars are in a spheroid whose longer
axes are coincident with the plane of the Milky Way. If this is
so, the close approach of pairs of stars should occur
preeminently in the Milky Way, and we should find the spirals
prevailingly in and near the Milky Way. This is precisely where
we do not find them. In fact, they seem to abhor the Milky Way.
The new stars, which are credibly explained as the products of
collisions of stars with nebulae, are found preeminently in the
Milky Way and almost negligibly in the regions outside of the
Milky Way. Again, the spirals are believed to be, on the whole,
of enormous size. They are too far away to let us measure their
distances by the usual methods, and they move too slowly on the
surface of the sphere to have let us determine their proper
motions. Slipher's recent work with a spectrograph seems to
show that the dozen spirals observed by him are moving with
high speeds of approach and recession; from 300 km. per second
approach in the case of the Andromeda nebula to 1,100 km. per
second recession in the case of several objects. If the spirals
are moving at random their speeds at right angles to the line
of sight must be even greater than their speeds of approach and
recession. Unless they are very distant bodies their proper
motions should be detected by observations extending over only
a few years. My colleague Curtis has this year compared recent
photographs of some 25 spirals with photographs of the same
object made by Keeler fifteen years ago. They reveal no
appreciable proper motions, or rotations. In this same interval
Neptune has revolved more than 30 degrees. Slipher has recently
measured the rotational speed of one "spindle" nebula, believed
to be a spiral. He finds it to be enormously rapid; no motions
in the solar system approach it in magnitude. The evidence is
to the effect that the spirals are in general very far away;[3]
perhaps on or beyond the confines of our stellar system, but
not certainly so. Accordingly, we are led to believe that the
spirals studied thus far have diameters 20 times or 100 times,
or in some cases several thousand times, the diameter of our
solar system. It is difficult to avoid the conclusion that in
general they are immensely more massive than is our solar
system. The spiral which has been assumed as the forerunner of
our system must have been of diminutive size as compared with
the larger and brighter spirals which we see to-day.

[2] It would seem that all rotating nebulae should in reality
possess some of the attributes of spiral motion. Whether the
spiral structure should be visible or invisible to a
terrestrial observer would depend upon the sizes and distances
of the nebulae, upon the distribution of materials composing
them, and perhaps upon other factors. See developed the
hypothesis that spiral nebulae owe their origin to the
collision of two nebulae. Collisions of this kind could readily
occur because of the enormous dimensions of the nebulae, and
motions of rotation and consequently spiral structure might
readily result therefrom. The abnormally high speeds of the
spiral nebulae are apparently a very strong objection to the

[3] Bohlin found a parallax of 0"17 for the Andromeda Nebula,
and Lampland thinks that Nebula N.G.G. 4594 has a proper motion
of approximately 0"05 per annum.

We are sadly in need of information concerning the constitution
of the spiral nebulae. Their spectra appear to be prevailingly
of the solar type, except that a very small proportion contain
some bright lines in addition to the continuous spectrum. So
far as their spectra are concerned, they may be great clusters
of stars, or they may consist each of a central star sending
its light out upon surrounding dark materials and thus
rendering these materials visible to us. The first alternative
is unsatisfactory, for all parts of spirals have hazy borders,
as if the structure is nebulous or consists of irregular groups
of small masses; and the second alternative is unsatisfactory,
for in many spirals the most outlying masses seem to be as
bright as masses of the same areas situated only one half as
far from the center, whereas in general the inner area should
be at least four times as bright as the outer area. All
astronomers are ready to confess that we do not know much about
the conditions existing in spiral nebulae.


Our Earth and Moon form a unique combination in that they are
more nearly of the same size than are any other planet and its
satellites in our system. It required a 26-inch telescope on
the Earth to discover the tiny moons of Mars; but an astronomer
on Mars does not need any telescope to see the Earth and Moon
as a double planet--the only double planet in the solar system.

According to the Kantian school of hypotheses the Earth and
Moon owe their unique character to the accident that two
centers of condensation--two nuclei--not very unequal in mass,
were formed close to each other and were endowed with or
acquired motions such that they revolved around each other.
They drew in the surrounding materials; one of the two bodies
got somewhat the advantage of the other in gravitational
attraction; it succeeded in building itself up more than the
other nucleus did; and the Earth and the Moon were the result.

According to the Laplacean hypothesis, on the contrary, the
Earth and Moon were originally one body, gaseous and in
rotation. This ball of gas radiated heat, diminished in size,
rotated more and more rapidly, and finally abandoned a ring of
nebulosity, which later broke up and eventually condensed into
one mass called the Moon. The central mass composed the Earth.
It is a curious fact that Venus, which is only a shade smaller
than the Earth, should not have divided into two bodies
comparable with the Earth and Moon. Have the tides on Venus
produced by the Sun always been strong enough to keep the
rotation and revolution periods equal, as they are thought to
be now, and thus to have given no opportunity for a rapidly
rotating Venus to divide into two masses?

A third hypothesis of the Moon's origin is due principally to
Darwin. He and Poincare have shown that a great rotating mass
of fluid matter, such as the Earth-Moon could be assumed to
have been, by cooling, contracting and increasing rotation
speed, would, under certain conditions thought to be
reasonable, become unstable and eventually divide into two
bodies revolving around their common center of mass, at first
with their surfaces nearly in contact. Here would begin to act
a tide-raising force which must have played, according to
Darwin's deductions, a most important part in the further
history of the Earth and Moon. The Earth would produce enormous
tides in the Moon, and the Moon much smaller tides in the
Earth. Both bodies would contract in size, through loss of
heat, and would try to rotate more and more rapidly. The two
rotating bodies would try to carry the matter in the tidal
waves around with the rest of the materials in the bodies, but
the pull of each body upon the wave materials in the other
would tend to slow down the speed of rotation. The tidal
resistance to rotation would be slight if the bodies at any
time were attenuated gaseous masses, for the friction within
the surface strata would be slight. Nevertheless, there would
eventually be a gradual slowing down of the Moon's rotation, a
gradual slowing down of the Earth's rotation, and a slow
increase in the distance between the two bodies. In other
words, the Moon's day, the Earth's day and our month would
gradually increase in length. Carried to its logical
conclusion, the Moon would eventually turn the same face to the
Earth, the Earth would eventually turn the same face to the
Moon, and the Earth's day and the Moon's day would equal the
month in length. The central idea in this logic is as old as
Kant: in 1754 he published an important paper in which he said
that tidal interactions between Earth and Moon had caused the
Moon to keep the same face turned toward us, that the Earth's
day was being very slowly lengthened, and that our planet would
eventually turn the same face to the Moon. Laplace, a
half-century later, proposed the action of such a force in
connection with the explanation of lunar phenomena, and
Helmholtz, just 100 years after Kant's paper was published,
lent his support to this principle; but Sir George Darwin has
been the great contributor to the subject. His popular volume,
"The Tides," devotes several chapters to the effects of tidal
friction upon the motions of two bodies in mutual revolution.
We must pass over the difficult and complicated intermediate
steps to Darwin's conclusions concerning the Earth and Moon,
which are substantially as follows: the Earth and Moon were
originally much closer together than they now are: after a very
long period of time, amounting to hundreds of millions of
years, the Moon will revolve around the Earth in 55 days
instead of in 27 days as at present; and the Moon and Earth
will then present the same faces constantly to each other. The
estimated period of time required, and the final length of day
and month, 55 days, are of course not insisted upon as accurate
by Darwin.

These tidal forces were unavoidably active, it matters not if
the Earth and Moon were originally one body, as Laplace and
Darwin have postulated, or originally two bodies, growing up
from two nuclei, in accordance with the Kantian school. Whether
these forces have been sufficiently strong to have brought the
Earth and Moon to their present relation, or will eventually
equalize the Moon's day, the Earth's day, and the month, is a
vastly more difficult question. Moulton's researches have cast
serious doubt upon this conclusion. All such investigations are
enormously difficult, and many questionable assumptions must be
made if we seek to go back to the Moon's origin, or forward to
its ultimate destiny.

Tidal waves, in order to be effective in reducing the
rotational speed of a planet, must be accompanied by internal
friction; and this requires that the planet be to some extent
inelastic. It was the view of Darwin and others that the
viscous state of the Earth and Moon permitted wave friction to
come into play. Michelson has recently proved that the Earth
has a high degree of elasticity. It deforms in response to
tidal forces, but quickly recovers from the action of these
forces. It therefore seems that the rate of tidal evolution of
the Earth-Moon system at present and in the future must be
extremely slow, and possibly almost negligible. What the
conditions within the Earth and Moon were in the distant past
is uncertain, but these bodies probably passed through viscous
stages which endured through enormously long periods of time.
No one seriously doubts that Jupiter, Saturn, Uranus and
Neptune are now largely gaseous, and that they will evolve,
through various degrees of viscosity, into the solid and
comparatively elastic state. It is natural to assume that the
Earth has already passed through an analogous experience.

The Moon turns always the same hemisphere toward the Earth.
Observations of Venus and Mercury are prevailingly to the
effect that those planets always turn the same hemispheres
toward the Sun. Many, and perhaps all, of the satellites of
Jupiter and Saturn seem to turn the same hemispheres always
toward their respective planets. This widely prevailing
phenomenon is no doubt due to a widely prevailing cause, which
astronomers have all but unanimously attributed to tidal


That an original mass actually divided to form the Earth and
Moon, according to the Laplacian or the Darwin-Poincare
principle, seems to be extremely doubtful, especially on
account of their diminutive sizes, and I greatly prefer to
think that the Earth and Moon were built up from two nuclei;
but that very much greater masses, masses larger on the average
than our Sun, composing highly attenuated stars, have divided
each into two masses to form many or most of our double stars,
I firmly believe. The two component stars would in such a case
at first revolve around each other with their surfaces almost
or quite in contact. Tidal forces would very gradually cause
the bodies to move in orbits of larger and larger size, with
correspondingly longer periods of revolutions, and the orbits
would become constantly more eccentric. While these processes
were under way the component bodies would be radiating heat and
growing smaller, and their spectra would be changing into the
more advanced types. We can not hope to watch such changes as
they occur, but we can, I think, find abundant illustrations of
these processes in the double stars. I have given reasons for
believing that one star in every two and one half, as a minimum
proportion, is not the single star which it appears to be to
the eye or in the telescope, but is a system of two or more
suns in mutual revolution. The formation of double stars,
therefore, is not a sporadic process: it is one of the
straightforward results of the evolutionary process.

Some of the variable stars offer strong evidence as to the
early life of the double stars. The so-called beta Lyrae
variables vary continuously in brightness, as if they consist
in each case of two stars so close together that their surfaces
are actually in contact in some pairs and nearly in contact in
others, so that from our point of view the two stars mutually
eclipse each other. When the two stars are in line with us we
have minimum brightness. When they have moved a
quarter-revolution farther, and the line joining them is at
right angles to our line of sight, so to speak, we have maximum
brightness. In every known case the beta Lyrae pairs of stars
have spectra of the very early types. Some of them even contain
bright lines in their spectra. The densities of these great
stars are known to be exceedingly low, in some cases much lower
on the average than that of the atmosphere which we breathe.

About 80 Algol variable stars are known. These are double stars
whose light is constant except during the short time when one
of the components in each system passes between us and the
other component. All double stars would be Algol variables if
we were exactly in the planes of their orbits. That so few
Algols have been observed amongst the tens of thousands of
double stars, is easily explained. The two component stars in
the few known Algol systems are so great in diameter, in
proportion to the size of their orbits, that eclipses are
observable throughout a wide volume of space, and the eclipses
are of long duration relatively to the revolution period. Their
densities are, so far as we have been able to determine them,
on an average less than 1/10th of the Sun's density. Let us
note well that their spectra, so far as we have been able to
determine them, are of the early types; mostly helium and
hydrogen stars, and a very few of the Class F, intermediate
between the hydrogen and solar stars. There are no known Algols
of the Classes G, K, and M: these stars are very condensed and
therefore small in size, as compared with stars of Classes B
and A; and the components of double stars of these classes are
on the average much denser and therefore smaller in size than
the components in Classes B and A double stars; the components
are much farther apart in Classes G to M doubles than in
Classes B and A doubles; and for these reasons eclipses in
Classes G to M doubles occur but rarely for observers scattered
throughout space. It is difficult to avoid the conclusion that
the components of double stars separate more and more widely
with the progress of time. The conclusions which we have
earlier drawn from visual double stars are in full harmony with
the argument.

It is agreed by all, I think, that tidal action has been
responsible for at least a part of the separation of the Earth
and Moon, for at least a part of the gradual separation of the
components of double stars, and for at least a part of the
eccentricity of their orbits. See's investigations of 25 years
ago led him to the conclusion that this force is sufficient to
account for all the observed separation of the components of
double stars, and for the well-known high eccentricities of
their orbits. In recent years Moulton and Russell have
seriously questioned the sufficiency of this force to account
for the major part of the separation and eccentricity in the
double star systems. I think, however, that if the tidal force
is not competent to account for the observed facts as
described, some other separating force or forces must be found
to supply the deficiency.


Does the condition of the Earth's interior give evidence on the
question of its origin? There are certain important facts which
bear upon the problem.

1. The evidence supplied by the volcanoes, by the hot springs,
and by the rise in temperature as we go down in all deep mines,
is unmistakably to the effect that there is an immense quantity
of heat in the Earth's interior. Near the surface the
temperature increases at the average of 1 degrees Centigrade
for every 30 meters of depth. If this rate were maintained we
should at 60 km. in depth arrive at a temperature high enough
to melt platinum, the most refractory of the known metals. What
the law of temperature-increase at great depths is we do not
know, but the temperature of the Earth's deep interior must be
very high.

2. The pressures in the Earth increase from zero at the surface
to the order of 3,000,000 atmospheric pressures at the center.
We know that rock structure, or iron or other metals, can be
slightly compressed by pressure, but the experiments at very
high pressures, notably those conducted by Bridgman, give no
indications that matter under such pressures breaks down and
obeys different or unknown laws. It should be said, however,
that laboratory pressure-effects alone are not a safe guide as
to conditions within the Earth, where high pressures are
accompanied by high temperature. Unfortunately it has not been
found possible to combine the high-temperature factor with the
high-pressure factor in the laboratory experiments. It is well
known that the melting points of metals, including rocks,
increase with increase of pressure; and although the
temperatures in the Earth's interior are very high, it is easy
to conceive that the materials of the Earth's interior are
nevertheless in the solid state, or that they act like solids,
because of the high pressures to which they are subjected.

3. The specific gravity of the entire Earth is 5.5 on the scale
of water as one, whereas the density of the stratified rocks
averages only 2.75; that is, the stratified rocks have but one
half the density of the Earth as a whole. The basaltic rocks
underlying the stratified attain occasionally the density 3.1,
and perhaps a little higher. It follows absolutely that the
density of the materials of the Earth's interior must be
considerably in excess of 5.5. If the interior is composed
chiefly of substances which are plentiful in the Earth's
surface strata, our choice of materials which principally
compose the interior is reduced to a few elements, notably the
denser ones.

4. The observed phenomena of terrestrial precession can not be
explained on the basis of an Earth with a thin solid surface
shell and a liquid interior, for the attractions of the Moon
and Sun upon the Earth's equatorial protuberance would cause
the surface shell to shift over the fluid interior, instead of
swinging the entire Earth.

5. If the Earth consisted of a thin solid shell upon a liquid
interior there would be tides in the liquid interior, the crust
would yield to these tides almost as if it were composed of
rubber, and the ocean tides would be only an insignificant
amount larger than the land tides. As a result we should not
see the ocean tides; their visibility depends upon the contrast
between the ocean tides and the land tides. If the Earth were
absolutely unyielding from surface to center the ocean tides
would be relatively 50 per cent. higher than we now see them.
The conclusion from these facts is that the Earth yields to the
tidal forces a little less than if it were a solid ball of
steel, supposing that the well-known rigidity and density
existed from surface to center of the ball. This result is
established by Darwin's and Schweydar's studies of ocean tides,
by studies of the tides in the Earth's surface strata made by
Hecker, Paschwitz and others, and by Michelson's recent
extremely accurate comparison of land and water tides.
Michelson's results establish further that the Earth is highly
elastic: though distortion is resisted, there is yielding, but
the original form is recovered quickly, almost as quickly as a
perfectly elastic body would recover.

6. Some 25 years ago it was discovered by Kustner that the
latitudes of points on the Earth's surface are changing slowly.
Chandler proved that these variations pass through their
principal cycle in a period of 427 days. The entire Earth
oscillates slightly in this period. The earlier researches of
Euler had shown that the Earth would have a natural oscillation
period of 305 days provided it were an absolutely rigid body.
Newcomb showed that the period of oscillation would be 441 days
if the Earth had the rigidity of steel. As the observed
oscillation requires 427 days, Newcomb concluded that the Earth
is slightly more rigid than steel.

7. The first waves from a very distant earthquake come to us
directly through the Earth. The observed speeds of transmission
are the greater, in general, the more nearly the earthquake
origin is exactly on the opposite side of the Earth from the
observer; that is, the speeds of transmission are greater the
nearer the center of the Earth the waves pass. Now, we know
that the speeds are functions of the rigidity and density of
the materials traversed. The observed speeds require for their
explanation, so far as we can now see, that the rigidity of the
Earth's central volume be much greater than that of steel, and
the rigidity of the Earth's outer strata considerably less than
that of steel. Wiechert has shown that a core of radius 4,900
km. whose rigidity is somewhat greater than that of steel and
whose average density is 8.3, overlaid by an outer stony shell
of thickness 1,500 km. and average density 3.2, would satisfy
the observed facts as to the average density of the Earth, as
to the speeds of earthquake waves, as to the flattening of the
Earth,--assuming the concentric strata to be homogeneous in
themselves,--and as to the relative strengths of gravity at the
Poles and at the Equator. The dividing line, 1,500 km. below
the surface--1,600 km. would be just one fourth of the way from
the surface to the center--places a little over half the volume
in the outer shell and a little less than half in the core.
Wiechert did not mean that there must be a sudden change of
density at the depth of 1,500 km., with uniform density 8.3
below that surface and uniform density 3.2 above that surface.
The change of density is probably fairly continuous. It was
necessary in such a preliminary investigation to simplify the
assumptions. The observational data are not yet sufficiently
accurate to let us say what the law of increase in density and
rigidity is as we pass from the surface to the center.

8. The phenomena of terrestrial magnetism indicate that the
distribution of magnetic materials in the Earth is far from
uniform or symmetrical; the magnetic poles are distant from the
Earth's poles of rotation; the magnetic poles are not opposite
each other; the lines of equal intensity as to all the magnetic
components involved run very irregularly over the Earth's
surface. There is reason to believe that iron in the deep
interior of the Earth, in view of its high temperature, is
devoid of magnetic properties, but we must not state this as a
fact. We know that iron is very widely, but very irregularly
spread throughout the Earth's outer strata. Whatever may be the
main factors in making the Earth a great magnet, to whatever
extent the rotation factor may be important, the Earth's
magnetic properties point strongly to a very irregular
distribution of magnetic materials in the outer strata where
the temperatures are below that at which magnetic materials
commonly lose their polarity.

9. Irregularities in the direction of the plumb-line and in the
force of gravity as observed widely and accurately over the
Earth's surface indicate that the surface strata are very
irregular as to density. To harmonize the observed facts
Hayford has shown the need of assuming that the heterogeneous
conditions extend down to a depth of 122 km. from the surface.
Below that level the Earth's concentric strata seem to be of
approximately uniform densities.

10. The radio active elements have been found by Strutt and
others in practically all kinds of rock accessible to the
geologists, but they are not found in significant quantities in
the so-called metals which exist in a pure state. These
radioactive elements are liberating heat. Strutt has shown that
if they existed down to the Earth's center in the same
proportion that he finds in the surface strata they would
liberate a great deal more heat than the body of the Earth is
now radiating to outer space. The conclusion is that they are
restricted to the strata relatively near the Earth's surface,
and are not in combination with the materials composing the
Earth's core. They have apparently found some way of coming to
the higher levels. Chamberlin suggests that as they liberate
heat they would raise surrounding materials to temperatures
above the normals for their strata, and that these expanded
materials would embrace every opportunity to approach the
surface of the Earth, carrying the radioactive substances with

The evidence is exceedingly strong, and perhaps irresistible,
to the effect that the Earth is now solid, or acts like a
solid, from surface to center, with possibly local, but on the
whole negligible, pockets of molten matter here and there; and
further, that the Earth existed in a molten, or at the least a
thickly plastic, state throughout a long part of its life. The
nucleus, whether gaseous or meteoric, from which I believe it
has grown, may have been fairly hot or quite cold, and the
materials which were successively drawn into the nucleus may
have been hot or cold: heat would be generated by the impacts
of the incoming materials; and as the attraction toward the
center of the mass became strong, additional heat would be
generated in the contraction process. The denser materials have
been able, on the whole, to gravitate to the center of the
structure, and the lighter elements have been able, on the
whole, to rise to and float upon the surface very much as the
lighter impurities in an iron furnace find their way to the
surface and form the slag upon the molten metal. The lighter
materials which in general form the surface strata are solid
under the conditions of solids known to us in every-day life.
The interior is solid or at least acts as a solid, because the
materials, though at high temperatures, are under stupendous
pressures. If the pressures were removed the deep-lying
materials would quickly liquefy, and probably even vaporize.

If the Earth grew from a small nucleus to its present size by
the extremely gradual drawing-in of innumerable small masses in
its neighborhood, the process would always be slow; much slower
at first when the small nucleus had low gravitating powers,
more rapid when the body was of good size and the store of
materials to draw upon plentiful,and gradually slower and
slower as the supply of building materials was depleted.
Meteoric matter still falls upon and builds up the Earth, but
at so slow a rate as to increase the Earth's diameter an inch
only after the passage of hundreds of millions of years. If the
Earth grew in this manner, the growth may now be said to be
essentially complete, through the substantial exhaustion of the
supply of materials.

Whether the Earth of its present size was ever completely
liquefied, that is, from center to surface, at one and the same
time, is doubtful. The lack of homogeneity, as indicated by the
plumb-line, gravity, terrestrial magnetism and radiaoctive
matter, extending in a perceptible degree down to 122 km., and
quite probably in lesser and imperceptible degree to a much
greater depth, is opposed to the idea.

Solidification would respond to the fall of temperature down to
the point required under the existing high pressures, and it is
probable that the solidification began at the center and
proceeded outwards. It is natural that the plastic state should
have developed and existed especially during the age of most
rapid growth, for this would be the age of most rapid
generation of heat. Later, while the rate of growth was
declining, the body could probably have solidified slowly and
successively from center out to surface. In later slow
depositions of materials, the denser substance would not be
able to sink down to the deepest strata: they must lie within a
limited depth and horizontal distance from where they fell, and
the outer stratum of the Earth would be heterogeneous in

The simplest hypothesis we can make concerning the Earth's deep
interior is that the chief ingredient is iron; perhaps a full
half of the volume is iron. The normal density of iron is 7.8,
and of rock formations about 2.8. If these are mixed, half and
half, the average density is 5.3. Pressures in the Earth should
increase the density and the heat in the Earth should decrease
the density. The known density of the Earth is 5.5. We know
that iron is plentiful in the Earth's crust, and that iron is
still falling upon the Earth in the form of meteorites. The
composition of the Earth as a whole, on this assumption, is
very similar to the composition of the meteorites in general.
They include many of the metals, but especially iron, and they
include a large proportion of stony matter. Iron is plentiful
in the Sun and throughout the stellar universe. Why should it
not be equally plentiful in the materials which have coalesced
to form the Earth? It is difficult to explain the Earth's
constitution on any other hypothesis.

The Earth's form is that which its rotation period demands.
Undoubtedly if the period has changed, the form has changed.
Given a little time, solids under great pressure flow quite
readily into new forms. Now any great slowing-down of the
Earth's rotation period within geological times would be
expected to show in the surface features. The strata should
have wrinkled, so to speak, in the equatorial regions and
stretched in the polar regions, if the Earth changed from a
spheroid that was considerably flatter than it now is, to its
present form. Mountains, as evidence of the folding of the rock
strata, should exist in profusion in the torrid zone, and be
scarce in or absent from the higher latitudes of the Earth.
Such differential effects do not exist, and it seems to follow
that changes in the Earth's rotation period and in its form
could have been only slight while the stratification of our
rocks was in progress.

Geologists estimate from the deposition of salt in the oceans,
and from the rates of denudation and sedimentation, that the
formation of the rock strata has consumed from 60,000,000 to
100,000,000 years. If the Earth had substantially its present
form 80,000,000 years ago we are safe in saying that the period
of time represented in the building up of the Earth from a
small nucleus to its present dimensions has been vastly longer,
probably reckoned in the thousands of millions of years.

For more than a century past the problem of the evolution of
the stars, including the solar system and the Earth, has
occupied the central place in astronomical thought. No one is
bold enough to say that the problem has been solved. The chief
difficulty proceeds from the fact that we have only one Earth,
one solar system and one stellar system available for tests of
the hypotheses proposed; we should like to test them on many
systems, but this privilege is denied us. However, the search
for the truth will undoubtedly proceed at an ever increasing
pace, partly because of man's desire to know the truth, but
chiefly, as Lessing suggested, because the investigator finds
an irresistible satisfaction in the process. There is always
with him the certainty that the truth is going to be
incomparably stranger and more interesting than fiction.




THE war in Europe has opened up a large field of trade in South
America. Three things especially stand in the way of its
development, viz., the absence of a proper credit system, the
failure to make goods of the kind demanded and third, the use
of our antiquated system of weights and measures, all the South
American countries employing the metric system. Of these three
obstructing influences, the first two are in a fair way to be
obviated soon; not so the last.

It is the use by our modern progressive country of an ancient
system of weights and measures which it is here proposed to
discuss and show up as an absurdity. Our present system is
organized and set forth in arithmetics under some fifteen
so-called "tables." These tables are all different and there is
no uniformity in any one table. Only one unit suggests
convenience in reductions, viz., hundredweight. It is easy to
reduce from pounds to hundredweight and vice versa. Some fifty
ratio numbers have to be memorized or calculated from other
memorized numbers to make the common needed reductions. History
shows that ancient Babylonia had tables superior to those now
in use, and ancient Britain a decimal scale which was crowded
out by our present system.

The metric system of weights and measures was developed in


Back to Full Books