Scientific American Supplement, No. 286
by
Various
Part 2 out of 2
in the class room by the teacher, is followed by a course in chemistry,
in which the members of the class perform the experiments for themselves
in the laboratory. And, notwithstanding the age, maturity, and previous
observation of the pupils, a great deal must be done both in the
laboratory and in the recitation room to be sure that all that happens
is seen--that the purpose is clearly held in the mind--that the reason
is fully understood.
With older pupils and greater facilities, however, the experiments
should be performed by the pupils themselves. Constant watchfulness is
necessary, it is true, to insure to the pupil the full educational
value of the experiment. With this watchfulness it can be done, and the
advantages are numerous. Among them are:
1. The learning of the use and care of apparatus.
2. The learning of methods of actual construction, from materials at
hand, of some of the simpler kinds of apparatus.
3. The learning of the importance of careful preparation. An experiment
may be performed in a few minutes before a class which has taken an hour
or more of time in its preparation. The pupil fully appreciates its
importance, and is in the best condition to remember it only when he
has had a part of the hard work attending that preparation. Again,
conditions under which an experiment is successfully performed are often
not appreciated when merely stated in words. "To prepare hydrogen gas,
pass a thistle tube and a delivery tube through a cork which fit tightly
in the neck of a bottle," etc., is simple enough. Let a pupil try with a
cork which does not fit tightly and he will never forget that condition.
4. The learning of the importance of following directions. Chemistry,
especially, is full of those cases where this means everything.
Sometimes, not often in experiments performed in school, however, it may
mean even life or death.
The time for experiments should be carefully considered. When performed
by the teacher they should be taken up during the recitation:
1. If used as a foundation to build upon, at the beginning of the
lesson.
2. If used as a summary, at the close.
3. They should be closely connected with the points which they
illustrate.
4. When very short, or when so difficult as to demand the whole
attention of the teacher, they may be given and afterward discussed. If
long or easy, they may be discussed while the work is going on. Changes
which take place slowly, as those which are brought about by the gradual
action of heat, for instance, are best taken up in this latter way.
5. Exceptions may be necessary, as when experiments which demand special
preparation immediately before they are presented are given when the
recitation begins, or cases in which experiments are kept until near the
close of a recitation, when the teacher finds that attention flags and
the lesson seems to have lost its interest to the pupils as soon as the
experiments have been given.
When performed by the pupils themselves, experiments should come before
the recitation as a part of the preparation for the work of the class
room.
Even in those cases in which the teacher performs the work, opportunity
should be given, from time to time, for the performing of the experiment
by the pupils themselves. This can be done in several ways. During the
course in physics here I am in the habit of leaving apparatus on the
table in my room for at least one day, often for a longer time, and of
giving permission to my class to perform the experiments for themselves
when their time permits and the nature of the experiment makes it an
advantage to get a nearer view than was possible in the class work. I
leave it to them to decide when to perform the experiments, or whether
it is to their advantage to take the time to perform them at all. I make
no attempt to watch either pupils or apparatus, although I would
often assist or explain at intermissions or during the afternoon. The
apparatus was largely used, and the effect on recitations was a good
one. For advanced pupils, and those who can be fully trusted, the plan
is a good one. The only question is the safety of the apparatus; each
teacher can decide for himself regarding the advisability of the plan
for his own school.
With smaller pupils their own safety may render it best to keep
apparatus out of their hands, except under the immediate direction of
the teacher. With all pupils that is, doubtless, the best plan where
chemicals are concerned.
Another method is to allow pupils to assist the teacher in the
preparation of experiments, to call occasionally upon members of the
class to come forward and give the experiment in the place of the
teacher, and to encourage home work relating to experiments. This latter
is often spontaneous on the part of older pupils, and can be brought
about with the smaller ones by the use of a little tact; many of the
toys of the present day have some scientific principle at bottom; let
the teacher find out what toys his young pupils have, and encourage them
to use them in a scientific way.
In whatever ways experiments be used, the class should be made to
consider the following elements as important in every case:
1. The purpose of the experiment. The same experiment may be performed
at one time for one purpose, at another time for another. The purpose
intended should be made the prominent thing, all others being
subordinated to it. Many chemical reactions, for instance, can be made
to yield either one of two or more substances for study or examination,
or use, while it may be the purpose of the experiment to close only one
of them.
2 The apparatus. All elements should be considered. The necessary should
be separated from that which may vary. In cases where the various parts
must have some definite relation to the others as regards size or
position, all that should be considered with care. In complex apparatus
the exact office of each part should be understood.
3. A clear understanding of what happens. To this I have already
referred.
4. Why it happens.
5. In what other way it might be made to happen. In chemistry almost
every substance can be prepared in several different ways. The common
method is in most cases made so by some consideration of convenience,
cheapness, or safety. Often only one method is considered in one place
in a text book. In a review, however, several methods can be associated
together. Tests, uses, etc., will vary, too, and should be studied with
that fact in view. In physics phenomena illustrating a given principle
can usually be made to take place in several different ways. Often very
simple apparatus will do to illustrate some fact for which complex and
costly apparatus would be convenient. In such case the study of the
experiment with that fact in view becomes important to us who need to
simplify apparatus as much as possible.
6. Special precautions which may be necessary. Some experiments always
work well, even in the hands of those not used to the work. Others are
successful--sometimes safe, even--only when the greatest care is taken.
Substances are used constantly in work in chemistry which are deadly
poisons, others which are gaseous and will pass through the smallest
holes. In physics the experiments usually present fewer difficulties of
this sort. But special care is necessary to complete success here.
7. Other things shown by the experiment. While the main object should
be kept in most prominent view in all experimental work, the fullest
educational value will come only when all that can be learned by the use
of an experiment is carefully considered.
In selecting just the work to be taken up with a given class of
children, attention must be paid to the selection of the appropriate
matter to be presented and the well adapted method of presenting it. The
following points should be carefully considered:
1. The matter must be adapted to the capacity of the child. This must be
true both as regards the quality and the quantity. The tendency will be
to teach too much when the matter presented is entirely new, but too
little in many cases where the pupil already knows the subject in a
general way. Matter is valuable only when given slowly enough to permit
of its being fully understood and memorized, while on the other hand
method is valuable only when it secures the development of attention and
the various faculties of the child's mind by presenting a sufficient
amount of the new.
2. The work must be based on what is already known. This, one of the
best known of the principles of teaching, is of at least as great
importance in physical science as in any other department of knowledge.
It seems to me in many cases to be more important here than elsewhere.
It is not necessary to reach each point by passing over every other
point usually considered. Lessons in electricity or sound, for instance,
can be given to children who have done nothing with other parts of
science. But a natural beginning must be made, and an orderly sequence
of lessons adopted. Children will not do what adults would find almost
impossible in covering gaps between lessons.
Science may be compared to a great temple. Pillars, each built of many
curiously joined stones, standing at the very entrance, represent the
departments of science so far as man has studied them. We need not dig
down and study the foundations with the children; we need not study
every pillar nor choose any particular one rather than some other; but
we must learn something of every stone--of each great fact--in the
pillar we select, be it ever so little. The original investigator climbs
to stones never before reached, or boldly ventures away into the dim
recesses beyond the entrance to bring back hints of what may be known
and believed a hundred years hence, perhaps. The exact investigator
measures each stone. Patiently and toilsomely scientific men examine
them with glass and reagent. We need not do this, but we must omit none
of the stones.
3. The work must be continuous. To continue the figure, the stones must
be considered in some regular order. One lesson in electricity, one in
sound, then one in some other department is injurious. We remember best
by associated facts, and, while with the child this is less so than with
the man, one great object of this work is to teach him to remember in
that way.
4. Experiments should never be performed for mere show. Of two
experiments which illustrate a fact equally well it is often best to
select the most striking and brilliant one. The attention and interest
of the child will be gained in this way when they would not be to so
great an extent in any other. The point of the experiment, however,
should never be lost sight of in attention to the merely wonderful in
it.
With older pupils, and especially with those who use books for
themselves and perform the experiments there considered, the fact that
experiments demand work, downright hard work, with care, and patience,
and perseverance, and courage, cannot be kept too prominently before
them.
5. Every lesson should have a definite object. Not the general value of
the experiment, but some _one thing_ which it shows should be the object
considered.
6. Each experiment should be associated with some truth expressed in
words. The experiment should be remembered in connection with a definite
statement in each case. The memory of either the experiment, or the
principle apart from the experiment, is a species of half knowledge
which should be avoided. An unillustrated principle must, when the
necessity arises, be stored in the memory; and in the systematic study
of books this necessity will often come. But we should never crowd this
abstract work on the memory unassisted by the suggestive concrete, when
the concrete aid is possible.
7. All that is taught should be true. It is not necessary to attempt to
exhaust a subject, nor to attempt to teach minute details regarding it
to the pupils in our schools, but it is necessary that every statement
given to the pupil to be learned and remembered should contain no
element of falsehood.
The student in mathematics experiences a feeling of growing strength and
power when he finds, in algebra, that the formula he used in arithmetic
in extracting a square root has grown in importance by leading
indirectly to a theorem of which it is only one particular case--a
theorem with a more definite proof, and a larger capability for use than
he had thought possible. When he finds a still simpler proof for the
binomial theorem in his study of the calculus, his feeling of increasing
power and the desire for still greater results deepens and intensifies.
Were he to find, on the contrary, that from a false notion of the means
to be used in making a thing simple, his teacher in arithmetic had
taught him what is false, we should approve his feeling of disgust and
disappointment. Early impressions are the most lasting, and the hardest
part of school work for the teacher is the unteaching of false ideas,
and the correcting of imperfectly formed and partially understood ideas.
I took a case from mathematics, the exact science, to illustrate this
point. But I must not neglect to notice the difference between that
subject and physical science. The latter consists of theories,
hypotheses, and so-called laws, supported by _observed facts_. The facts
remain, but time has overthrown many of the hypotheses and theories, and
it will doubtless overthrow more and give us something better and truer
in their place. While a careful distinction between what is known and
what is believed is necessary, I should always class the teaching of
accepted theories and hypotheses with the teaching of the true.
But teachers, with more of imagination than good sense, teach
distinctions which do not exist, generalizations which do not
generalize, and do incalculable mischief by so doing.
8. Experimental work should be thoroughly honest as to conditions and
results. If an experiment is not the success you expected it would be,
say so honestly, and if you know why, explain it. The pupil should be
taught to know just what _is_, theory or expectation to the contrary
notwithstanding. Discoveries in physical science have often originated
in a search for the reason for some unexpected thing.
The relation of the study of science to books on science should be
considered. For the work done with pupils before they are given books to
use for themselves, any attempt to follow a text book is to be deplored.
The study of the properties of matter, for instance, would be a fearful
and wonderful thing to set a class of little ones at as a beginning in
scientific work. Just what matter, and force, and molecules, and atoms
are may be well enough for the student who is old enough to begin to use
a book, but they would be but dry husks to a younger child. Many of the
careful classifications and analyses of topics in text books had far
better be used as summaries than in any other way; and a definition is
better when the pupil knows it is true than when he is about to find out
whether it is or not.
An ideal course in science would be one in which nothing should be
learned but that found out by the observation of the pupil himself under
the guidance of the teacher, necessary terms being given, but only when
the thing to be named had been considered, and the mind demanded the
term because of a felt need. Practically such a method is impossible in
its fullest sense, but a closer approach to it will be an advantage.
Among the numerous good results which will follow the study of physical
science are the following:
1. The cultivation of all the faculties of the child in a natural order,
thus making him grow into a ready, quick, and observing man. Education
in schools is too often shaped so as to repress instead of cultivate the
instinctive desire for the _knowledge of things_ which is found in every
child.
2. The mechanical skill which comes from the preparation and use of
apparatus.
3. The ability to follow directions.
4. The belief in stated scientific facts, the understanding of
descriptions, diagrams, etc.
5. The habitual scientific use of events which happen around us.
6. The study of the old to find the new. The principle of the telephone,
for instance, is as old as spoken language. The mere[1] pulses in the
air--carrying all the characteristics of what you say--may set in
vibration either the drum of my ear, or a disk of metal. How simple--and
how simple all true science is--when we understand it.
[Transcribers note 1: corrected from 'more']
8. The cultivation of the scientific judgment, and the inventive powers
of the mind. One great original investigator, made such by the direction
given his mind in one of our common schools, would be cheaply bought at
the price of all that the study of science in our schools will cost for
the next quarter of a century.
8. Honesty. If there is a study whose every tendency is more in the
direction of honesty and truthfulness--both with ourselves and with
others--than is the study of experimental science, I do not know what it
is.
Physical science, then, will help in making men and women out of our
boys and girls. It is worthy of a fair, earnest trial everywhere.
A few minutes each day in which a class or a school study science in
some of the ways I have indicated will give a knowledge at the end of a
term or a year of no mean value. The time thus spent will have rested
the pupils from their books, to which they will return refreshed, and
instead of being time lost from other study the work will have been made
enough more earnest and intense to make it again.
Apparatus for illustrating many of the ordinary facts of physics can be
devised from materials always at hand. Many more can be made by any
one skilled in the use of tools. In chemistry, the simplicity of the
apparatus, and comparative cheapness of ordinary chemicals, make the use
of a large number of beautiful and instructive experiments both easy and
cheap.
A nation is what its trades and manufactures--its inventions and
discoveries--make it; and these depend on its trained scientific men.
Boys become men. Their growing minds are waiting for what I urge you
to offer. Science has never advanced without carrying practical
civilization with it--but it has never truly advanced save by the use of
the experimental method. _And it never will_.
Let us then look forward to the time when our boys and young men--our
girls and young women--shall extend the boundaries of human knowledge by
its use, fitted so to do by what we may have done for them.
* * * * *
GEOGRAPHICAL SOCIETY OF THE PACIFIC.
This society is a recent organization, the objects of which are to
encourage geographical exploration and discovery; to investigate and
disseminate geographical information by discussion, lectures, and
publications; to establish in this, the chief maritime city of the
Western States, for the benefit of commerce, navigation, and the
industrial and material interests of the Pacific slope, a place where
the means will be afforded of obtaining accurate information not only of
the countries bordering on the Pacific ocean, but of every part of the
habitable globe; to accumulate a library of the best books on geography,
history, and statistics; to make a collection of the most recent maps
and charts--especially those which relate to the Pacific coast, the
islands of the Pacific and the Pacific ocean--and to enter into
correspondence with scientific and learned societies whose objects
include or sympathize with geography.
The society will publish a bulletin and an annual journal, which will
interchange with geographical and other societies. Monthly meetings are
to be held, at which original papers will be read or lectures be
given; and to which, as well as to the entertainments to distinguished
travelers, to the conversazioni, and to the informal evenings, the
fellows of the society will have the privilege of introducing their
friends. The initiation fee to the society is $10; monthly dues $1; life
fellowship $100.
At a meeting held at the Palace Hotel on the 12th May, the following
gentlemen were elected for the ensuing year: President, Geo. Davidson;
Vice-Presidents, Hon. Ogden Hoffman, Wm. Lane Booker, H.B.M. Consul, and
John R. Jarboe; Foreign Corresponding Sec., Francis Berton; Home Cor.
Sec., James P. Cox; Treas., Gen. C. I. Hutchinson; Sec'y, C. Mitchell
Grant, F.R.G.S. The council is composed of the following: Hon. Joseph W.
Winans, Hon. J.F. Sullivan, Ralph C. Harrison, A.S. Hallidie, Thos. E.
Stevin, F.A.G.S., W.W. Crane, Jr., W.J. Shaw, C.P. Murphy, Thos. Brice,
Edward L.G. Steele, Gerrit L. Lansing, Joseph D. Redding. The Trustees
are Geo. Davidson, Wm. Lane Booker, Hon. Jno. S. Hager, Geo. Chismore,
M.D., Selim Franklin.
* * * * *
THE BEHRING'S STRAITS CURRENTS.
It will be remembered that a short time since we mentioned the fact that
W.H. Dall, of the U. S. Coast Survey, who has passed a number of years
in Alaskan waters, on Coast Survey duty, denied the existence of any
branch of the Kuro Shiwo, or Japanese warm stream, in Behring's Straits.
That is, he failed to find evidence of the existence of any such
current, although he had made careful observations. At the islands in
Behring's Straits, his vessel had sailed in opposite directions with ebb
and flood tide, and he thought the only currents there were tidal in
their nature. The existence or non-existence of this current is an
important point in Arctic research on this side of the continent.
At the last meeting of the Academy of Sciences, Prof. Davidson, of the
U. S. Coast Survey, author of the "Alaska Coast Pilot," refuted Dr.
Dall's opinion of the non-existence of a branch of the Kuro Shiwo, or
Japanese warm stream, from the north Pacific into the Arctic Ocean,
through Behring's Straits. He said that in 1857 he gave to the Academy
his own observations, and recently he had conferred with Capt. C.L.
Hooper, who commanded the U. S. steamer Thomas Corwin, employed as a
revenue steam cruiser in the Arctic and around the coast of Alaska.
Capt. Hooper confirms the opinions of all previous navigators, every one
of which, except Dr. Dall, say that a branch of this warm stream passed
northward into the Arctic through Behring's Strait. It is partly
deflected by St. Lawrence Island, and closely follows the coast on the
Alaskan side, while a cold current comes out south, past East Cape
in Siberia, skirting the Asiatic shore past Kamschatka, and thence
continues down the coast of China. He said ice often extended several
miles seaward, from East Cape on the Asiatic side of Behring Strait,
making what seamen call a false cape, and indicating cold water, while
no such formation makes off on the American side, where the water is
12 degrees warmer than on the Asiatic shore off the Diomede islands,
situated in the middle of Behring's Strait, the current varies in
intensity according to the wind.
Frequently it is almost nothing for several days, when after a series of
southerly winds the shallow Arctic basin has been filled, under a heavy
pressure, with an unusual volume of water, and a sudden change to
northerly winds, makes even a small current setting southward for a few
days, just as at times the surface currents set out our Golden Gate
continuously for 24 and 48 hours, as shown by the United States Coast
Survey tide gauges. Whalers report that the incoming water then flows
in, under the temporary outflowing stream.
Old trees, of a variety known to grow in tropical Japan, are floated
into the Arctic basin as far as past Point Barrow, on the American side,
but none are found on the Asiatic side, or near Wrangell Land, where a
cold stream exists, and ice remains late in the season. On the northern
side of the Aleutian islands are found cocoanut husks and other tropical
productions stranded along the beaches. The American coast of Alaska
has a much warmer climate than the Asiatic coast of Siberia, and the
American timber line extends very far north. The ice opens early in the
season on the American side, and invariably late on the Asiatic.
Capt. C. L. Hooper says that when just north of Behring's Strait, off
the American coast, in the Arctic basin, the U.S. steamer Thomas Corwin,
when becalmed for 24 hours, drifted 40 miles to the northward. From
all these, and other facts, and the unanimous testimony of American
whalemen, who have for years spent many months annually in the Arctic,
and from his own observations, he argued that a branch of the Kuro-Shiwo
or Japanese warm stream, unquestionably runs northward through Behring's
Strait into the Arctic basin along the northwestern coast of Alaska.
Prof. Davidson then called to mind the testimony in regard to the
existence of Plover Island, between Herald Island and Wrangell Land,
which he said was first made public through this academy. The evidence
of Capts. Williams and Thomas Long were recited and highly praised. One
of the officers of Admiral Rodgers' expedition climbed to near the top
of Herald Island, at a time of great refraction, when probably a false
horizon existed, and hence did not see Plover Island, although Wrangell
Land was in sight.
Prof. Davidson thinks all the authorities are against Dr. Dall, who
attributes the warm current he observed on the American coast to water
from the Yukon River and to the large expanse of shallow water exposed
to the sun's rays. As Dall's observations only covered a few days of
possibly exceptional weather, and the whalers and Captain Hooper's cover
vastly longer periods, and whalers all say it is a pretty hard thing to
beat southward through Behring's Strait, owing to the northerly current
setting into the Arctic, we are forced to the conclusion that Dr.
Dall has mistaken the exception for the rule, and his conclusions are
therefore erroneous. When, in 1824, Wrangell went north, he, like
others, always found broken ice and considerable open water. In 1867,
when Capt. Thomas Long made his memorable survey of the coast of
Wrangell Land, the season was an exceptionally open one, and in
California we had heavy rains, extending into July.
* * * * *
EXPERIMENTAL GEOLOGY.
ARTIFICIAL PRODUCTION OF CALCAREOUS PISOLITES AND OOLITES.
Mr. Stanislas Meunier communicates to _Le Nature_ an account of some
interesting specimens of globular calcareous matter, resembling
pisolites or peastones both in appearance and structure, which were
accidentally formed as follows: The Northern Railway Company, France,
desiring to purify some calciferous water designed for use in steam
boilers, hit upon the ingenious expedient of treating it with lime water
whose concentration was calculated exactly from the amount of lime
held in the liquid to be purified. The liquids were mixed in a vast
reservoir, to which they were led by parallel pipes, and by which they
were given a rapid eddying motion. The transformation of the
bicarbonate into neutral carbonate of lime being thus effected with
the accompaniment of a circling motion, the insoluble salt which
precipitated, instead of being deposited in an amorphous state, hardened
into globules, the sizes of which were strictly regulated by the
velocity of the currents. Those that have been formed at one and the
same operation are uniform, but those formed at different times vary
greatly--their diameters varying by at least one millimeter to one and
a half centimeters. The surface of the smaller globules is smooth, but
that of the larger ones is rough. Even by the naked eye, it may be
seen that both the large and small globules are formed of regularly
superposed concentric layers. If an extremely thin section be made
through one of them it is found that the number of layers is very great
and that they are remarkably regular (A). By the microscope, it has been
ascertained that each layer is about 0.007 of a millimeter in thickness.
On observing it under polarized light the calcareous substance is
discovered to be everywhere crystallized, and this suggests the question
whether the carbonate has here taken the form of aragonite or of
calcite. Examination has shown it to be the latter. The density of the
globules (2.58) is similar to that of ordinary varieties of calcite. It
is probable that if the operation were to take place under the influence
of heat, under the conditions above mentioned, aragonite would be
formed. It is hardly necessary to dwell upon the possible geological
applications of this mode of forming calcareous oolites and pisolites.
ON CRYSTALS OF ANHYDROUS LIME.
Some time ago it was discovered that some limestone, which had been
submitted for eighteen months to a heat of nearly 1,000 degrees in
the smelting furnaces of Leroy-Descloges (France), had given rise to
perfectly crystallized anhydrous lime. Figure C shows three of these
crystals magnified 300 diameters. It will be noticed that they have a
striking analogy with grains of common salt. They are, in fact, cubes
(often imperfect), but do not polarize light, as a substance of the
first crystalline system should. However, it is rarely the case that the
crystals do not have _some_ action on light. Most usually, when the two
Nicol prisms are crossed so as to cause extinction, the crystals present
the appearance shown at D. That is to say, while the central portion
is totally inactive there are seen on the margins zones which greatly
brighten the light.
[Illustration]
A and B.--Calcareous Pisolites and Oolites produced artificially.
A.--External aspect and section of a Pisolite. B.--Details of internal
structure as seen by the microscope.
C and D.--Crystals of anhydrous Lime obtained artificially. C.--Crystals
seen under the microscope in the natural light. D.--Crystals seen under
the microscope in polarized light.
The phenomenon is explained by the slow carbonization of the anhydrous
lime under the influence of the air; the external layers passing to the
state of carbonate of lime or Iceland spar, which, as well known, has
great influence on polarized light. This transformation, which takes
place without disturbing the crystalline state, does not lead to any
general modification of the form of the crystals, and the final product
of carbonization is a cubic form known in mineralogical language as
_epigene_. As the molecule of spar is entirely different in form
from the molecule of lime, the form of the crystal is not absolutely
preserved, and there are observed on the edges of the epigene crystal
certain grooves which correspond with a loss of substance. These grooves
are quite visible, for example, on the crystal to the left in Fig. D.
Up to the present time anhydrous lime has been known only in an
amorphous state. The experiment which has produced it in the form noted
above would doubtless give rise to crystallized states of other earthy
oxides likewise, and even of alkalino-earthy oxides.
COCCIDAE.
[Footnote: A paper recently read before the California Academy of
Sciences.]
By DR. H. BEHR.
With the exception of Hymenoptera there is no group of insects that
interfere in so many ways in good and evil with our own interests, as
that group of Homoptera called Coccidae.
But while the Hymenoptera command our respect by an intellect that
approaches the human, the Coccus tribe possesses only the lowest kind of
instinct, and its females even pass the greater part of their lives in
a mere vegetation state, without the power of locomotion or perception,
like a plant, exhibiting only organs of assimilation and reproduction.
But strange to say, these two groups, otherwise so very dissimilar,
exhibit again a resemblance in their product. Both produce honey and
wax.
It is true, the honey of this tribe is almost exclusively used by the
ants. But I have tasted the honey-like secretion of an Australian
lecanium living; on the leaves of Eucalyptus dumosus; and the manna
mentioned in Scripture is considered the secretion of Coccus manniparus
(Ehrenberg) that feeds on a tamarix, and whose product is still used by
the native tribes round Mount Sinai.
Several species of Coccides are used for the production of wax; many
more, among which the Cochenill, for dyes.
All these substances can be obtained in other ways, even the Cochenill
is to a great extent superseded by aniline dyes, but in regard to one
production, indispensable to a great extent, we are entirely dependent
on some insects of this family; it is the Shellac, lately also found in
the desert regions around the Gila and Colorado on the Larrea Mexicana.
You will remember that excellent treatise on this variety of Shellac,
written by Professor J.M. Stillman at Berkeley, on its chemical
peculiarities.
But all these different forms of utility fall very lightly in weight,
and can not even be counted as an extenuating circumstance, when we
compare them to the enormous evils brought on farmer and gardener by the
hosts of those Coccides that visit plantations, hothouses, and orchards.
To combat successfully against these insect-pests we have first to study
their habits and then adapt to them our remedies, which you will see
are more effective when well administered than those which we possess
against insect pests of other classes.
I give here only the outlines of their natural history, peculiarities
that are common to all, for it would be impossible to go into detail.
Where there are exceptions of practical importance I will mention them.
In countries with a well defined winter the winged males appear as
soon as white frosts are no more usual, and copulate with the unwieldy
limbless female, that looks more like a gall or morbid excrescence, than
a living animal. Shortly after the young ones are perceptible near the
withered body of their mother, covered by waxy secretions that look
somewhat like a feathery down.
These young ones are lively enough, they move about with agility, and
it is not till high summer that they fasten themselves permanently, and
lose feet and antennae, organs of locomotion and perception that are no
more of any use to them. (There is a slight difference in this regard
between different genera, as for instance, Coccus and Dorthesia retain
these organs in different degrees of imperfection, Lecanium and
Aspidiotus losing every trace of them.)
In this limbless, senseless state the females remain fall and winter.
Toward the end of winter these animated galls begin to swell, and those
containing males enter the state of the chrysalis, from which the males
emerge at the beginning of the warm season and fecundate the gall-like
females, which undergo neither chrysalis state nor any other change, but
die, or we may call it dissolve into their offspring, for there scarcely
remains anything of them, except a pruinous kind of down, after having
given birth to the young ones.
Now we come to the practical deduction from these facts. It is clear
that the only time when the scalebug can emigrate and infest a new
tree is the time when it is a larva, that is, when it has the power of
locomotion. In countries with a pronounced winter this time begins
much later than with us, but it ends about the same time, that is, the
beginning of August. I have seen the male of Aspidiotus in February, so
that the active larva may be expected in March, and the active Lecanium
Hesperidum I have seen last year, June 27, at Colonel Hooper's ranch in
Sonoma County. We may safely fix the time of the active scalebug from
March to August.
Notwithstanding the agility of the young scalebug, the voyage from one
tree to another, considering the minute size of the traveler, is an
undertaking but seldom succeeding, but one female bug, if we take
into account its enormous fertility, is sufficient to cover with its
grandchildren next year a tree of moderate size.
Besides there is another and much more effective way of transmigration
by the kind assistance of the ant who colonizes the scalebug as well for
its wax as it colonizes the Aphis for its honey. Birds on their feathers
and the gardener himself on his dress contribute to spread them.
But even the ant can not transplant the scalebug when it is once firmly
fixed by its rostrum.
It is evident, therefore, that the time for the application of
insecticides is the time when all the scalebugs are fixed, that is about
the end of July or beginning of August. All previous application will
clean the tree or plant only for a time, and does not prevent a more or
less numerous immigration from the neighboring vegetation, especially if
an ant-hill is not far off.
As to the insecticide, there are to be applied two very effective ones,
each with its advantages and disadvantages.
1. Petroleum and its different preparations.
2. Lye or soap.
The petroleum is the best disinfectant. It can safely be applied to any
cutting or stem, as long as it is not planted, but is one of the most
invidious substances when applied to vegetation in the garden, or
fields. If effectively applied, it can not be prevented from running
down the bark of the tree and entering the ground, where every drop
binds a certain amount of earth to an insoluble substance, in which
state it remains for ever. With every application the quantity of these
insoluble compounds is augmented and sterility added.
If I am not mistaken, it was near Antwerp--at least I am certain it was
in Belgium--where the first experience of this kind is recorded.
In France, preparations of coal tar have been recommended and have
been lately used in the form of a paint. May be that in this form the
substance is not so apt to enter into combinations with the soil. At any
rate, the method is of too recent a date to permit any conclusions about
the final result of these applications, as the invidious nature of the
substance produces, by gradual accumulation, its effects, which are not
perceived until they are irreparable.
2. Lye or soap. The application of these insecticides requires more
care, and is therefore more troublesome. But instead of attracting
fertility from the soil, they add to it. In Southern Europe soap
and water has been for many years the remedy against the Lecanium
Hesperidum. The method applied by the farmers in Portugal, as described
to me by Dr. Bleasdale, is perhaps the most perfect one. The Portuguese
have very well observed that the colonization of scalebugs always begins
at the lowest end of the trunk and pretend, therefore, that the scalebug
comes out of the ground. This, of course, is not the case, but may their
interpretation be an error, they have been practical enough in utilizing
their observation about the invasion beginning near the roots. They
knead a ring of clay round the tree, in which ring the soap water runs
when they wash the tree, and besides, they fill frequently the little
ditch formed by this ring.
This arrangement of course is only possible in climates of a rainy
summer.
As it is our object to make our knowledge as available as possible for
practical purposes, I repeat for the benefit of cultivators the advice,
without repeating the reasoning:
1. Use the petroleum for disinfecting imported trees and cuttings:
2. Use soap for cleaning trees planted in your orchard.
3. If you must use the petroleum in your garden, use it in August, when
a single application is sufficient.
* * * * *
AGRICULTURAL ITEMS.
The exportation of dried apples from this country to France has greatly
increased of late years, and now it is said that a large part of this
useful product comes back in the shape of Normandy cider and light
claret.
A.B. Goodsell says in the _New York Tribune_: "Put your hen feed around
the currants. I did this twice a week during May and June, and not a
currant worm was seen, while every leaf was eaten off other bushes 150
feet distant, and not so treated."
Buckwheat may be made profitable upon a piece of rough or newly cleared
ground: No other crop is so effective in mellowing rough, cloddy land.
The seed in northern localities should be sown before July 12; otherwise
early frosts may catch the crops. Grass and clover may sometimes be sown
successfully with buckwheat.
The London News says: "Of all poultry breeding, the rearing of the goose
in favorable situations is said to be the least troublesome and most
profitable. It is not surprising, therefore, that the trade has of late
years been enormously developed. Geese will live, and, to a certain
extent, thrive on the coarsest of grasses."
When a cow has a depraved appetite, and chews coarse, indigestible
things, or licks the ground, it indicates indigestion, and she should
have some physic. Give one pint and a half of linseed oil, one pound of
Epsom salts, and afterward give in some bran one ounce of salt and the
same of ground ginger twice a week.
Asiatic breeds of fowl lay eggs from deep chocolate through every shade
of coffee color, while the Spanish, Hamburg, and Italian breeds are
known for the pure white of the eggshell. A cross, however remote, with
Asiatics, will cause even the last-named breeds to lay an egg slightly
tinted.
In setting out currant bushes care should be exercised not to place any
buds under ground, or they will push out as so many suckers. Currants
are great feeders, and should be highly manured. To destroy the worm,
steep one table-spoonful of hellebore in a pint of water, and sprinkle
the bushes. Two or three sprinklings are sufficient for one season.
Mr. Joseph Harris, of Rochester, makes a handy box for protecting melons
and cucumbers from insect enemies. Take two strips of board of the
required size, and fasten them together with a piece of muslin, so the
muslin will form the top and two sides of the box. Then stretch into
box form by inserting a small strip of wood as a brace between the two
boards. This makes a good, serviceable box, and, when done with for the
season, it can be packed into a very small space, by simply removing the
brace and bringing the two board sides together. As there is no patent
on the contrivance, anybody can make the boxes for himself.
Mr. C. S. Read recently said before the London Fanners' Club: "American
agriculturists get up earlier, are better educated, breed their stock
more scientifically, use more machinery, and generally bring more
brains to bear upon their work than the English farmer. The practical
conclusion is, that if farmers in England worked hard, lived frugally,
were clad as meanly as those of the States, were content to drink filthy
tea three times a day, read more and hunted less, the majority of them
may continue to live in the old country."--_N. E. Farmer_.
* * * * *
TIMBER TREES.
A paper was read by Sir R. Christison at the last meeting of the
Edinburgh Botanical Society upon the "Growth of Wood in 1880." In a
former paper, he said, he endeavored to show that, in the unfavorable
season of 1879, the growth of wood of all kinds of trees was materially
less than in the comparatively favorable season of 1878. He had now to
state results of measurements of the same trees for the recent favorable
season of 1880. The previous autumn was unfavorable for the ripening of
young wood, and the trees in an unprepared condition were exposed during
a great part of December, 1879, to an asperity of climate unprecedented
in this latitude. This might have led one to expect a falling off in the
growth of wood, and it appeared, from comparison of measurements, that,
with very few exceptions, the growth of wood last year was even more
below the average of favorable years than that of the bad year, 1879.
Thus, in fifteen leaf-shedding trees of various species, exclusive of
the oak, the average growth of trunk girth in three successive years
was: 1878, 8-10ths; 1879, 45-100ths; 1880, 3-10ths and a half. In
four specimens of the oak tribe, the growth was: 1878, 8-10ths; 1879,
77-100ths; 1880, 54-100ths. In twenty specimens of the evergreen
Pinaceae the growth was: 1878, 8-10ths; 1879, 7-10ths; 1880, 6-10ths and
a half. After giving details in regard to particular trees, Sir Robert
stated, as general deductions from his observations, that leaf-shedding
trees, exclusive of the oak, suffered most; that the evergreen Pinaceae
suffered least; and that there was some power of resistance on the part
of the oak tribe which was remarkable, the power of resistance of the
Hungary oak being particularly deserving of attention. In another
communication on the "extent of the season of growth," Sir Robert
stated, as the result of observations on five leaf-shedding and five
evergreen trees, that in the case of the former, even in a fine year,
the growth of wood was confined very nearly, if not entirely, to the
months of June, July, and August; while in the case of the latter growth
commenced a month sooner, terminating, however, about the same time. Mr.
A. Buchan said it was proposed that the inquiry should be taken up more
extensively over Scotland.
* * * * *
MEDICAL USES OF FIGS.--Prof. Bouchut speaks (_Comptes Rendus_) of some
experiments he has made, going to show that the milky juice of the
fig-tree possesses a digestive power. He also observed that, when some
of this preparation was mixed with animal tissue, it preserved it
it from decay for a long time. This fact, in connection with Prof.
Billroth's case of cancer of the breast, which was so excessively foul
smelling that all his deodorizers failed, but which, on applying a
poultice made of dried figs cooked in milk, the previously unbearable
odor was entirely done away with, gives an importance to this homely
remedy not to be denied.--_Medical Press and Circ._
* * * * *
BLOOD RAIN.
The sensibilities of ignorant or superstitious people have at various
times been alarmed by the different phenomena of so-called blood, ink,
or sulphur rains. Ehrenberg very patiently collected records of the most
prominent instances of these, and published them in his treatise on the
dust of trade winds. Some, it is known, are due to soot; others, to
pollen of conifers or willows; others, to the production of fungi and
algae.
Many of the tales of the descent of showers of blood from the clouds
which are so common in old chronicles, depends, says Mr. Berkeley, the
mycologist, upon the multitudinous production of infusorial insects or
some of the lower algae. To this category belongs the phenomenon known
under the name of "red snow." One of the most peculiar and remarkable
form, which is apparently virulent only in very hot seasons, is caused
by the rapid production of little blood-red spots on cooked vegetables
or decaying fungi, so that provisions which were dressed only the
previous day are covered with a bright scarlet coat, which sometimes
penetrates deeply into their substance. This depends upon the growth of
a little plant which has been referred to the algae, under the name
of _Palmellae prodigiosa_. The rapidity with which this little plant
spreads over meat and vegetables is quite astonishing, making them
appear precisely as if spotted with arterial blood; and what increases
the illusion is, that there are little detached specks, exactly as if
they had been squirted from a small artery. The particles of which the
substance is composed have an active molecular motion, but the morphosis
of the production has not yet been properly observed. The color of the
so-called "blood rain" is so beautiful that attempts have been made
to use it as a dye, and with some success; and could the plant be
reproduced with any constancy, there seems little doubt that the color
would stand. On the same paste with the "blood-rain" there have been
observed white, blue, and yellow spots, which were not distinguishable
in structure and character.
* * * * *
TOPICAL MEDICATION IN PHTHISIS.
Dr. G.H. Mackenzie reports in the _Lancet_ an acute case of phthisis
which was successfully treated by him by causing the patient to respire
as continuously as possible, through a respirator devised for the
purpose, an antiseptic atmosphere. The result obtained appears to bear
out the experiments of Schueller of Greifswald, who found that animals
rendered artificially tuberculous were cured by being made to inhale
creosote water for lengthened periods. Intermittent spraying or inhaling
does not produce the same result. In order to insure success the
application to the lungs must be made _continuously_. For this purpose
Dr. Mackenzie has used various volatile antiseptics, such as creosote,
carbolic acid, and thymol. The latter, however, he has discarded
as being too irritating and inefficient. Carbolic acid seems to be
absorbed, for it has been detected freely in the urine after it had been
inhaled; but this does not happen with creosote. As absorption of the
particular drug employed is not necessary, and therefore not to be
desired, Dr. Mackenzie now uses creosote only, either pure or dissolved
in one to three parts of rectified spirits. "Whether," says he, "the
success so far attained is due to the antidotal action of creosote and
carbolic acid on a specific tubercular neoplasm, or to their action as
preventives of septic poisoning from the local center in the lungs,
it is certain that their continuous, steady use in the manner just
described has a decidedly curative action in acute phthisis, and is
therefore, worthy of an extended trial."
* * * * *
ON THE LAW OF AVOGADRO AND AMPERE.
The Scientific American Supplement of May 14,1881, contains, under this
head, Mr. Wm. H. Greene's objections to my demonstration (in No. 270
of the same paper) of the error of Avogadro's hypothesis. The most
important part of my argument is based on the evidence afforded by the
compound cyanogen; and Mr. Greene, directing his attention to this
subject in the first place, states that because cyanogen combines
with hydrogen or with chlorine, without diminution of volumes, I have
concluded that the hypothesis falls to the ground. This statement has
impressed me with the conviction that Mr. Greene has failed to perceive
the difficulty which is at the bottom of the question, and I will,
therefore, present the subject more fully and comprehensively.
The molecule of any elementary body is, on the ground of the hypothesis,
assumed to be a compound of two atoms, and the molecule of carbon
consequently C_2=24; that of nitrogen N_2=28. Combination of the two,
according to the same hypothesis, takes place by substitution; the
atoms are supposed to be set free and to exchange places, forming a
new compound different from the original only in this: that each new
particle contains an atom of each of the two different substances, while
each original particle consists of two identical atoms. The product is,
therefore, assumed to be, and can, under the circumstances, be no other
than particles of the composition CN and weight 26. These particles are
molecules, according to the definition laid down, just as C_2 and N_2;
but there is this essential difference, that the specific gravity of
cyanogen gas, 26, coincides with the molecular weight, while the assumed
molecular weight, N_2=28, is twice as great as the specific gravity of
the gas, N=14.
In using the term molecular weight, it is to be remembered that it does
not express the weight of single molecules, but only their relative
weight, millions of millions molecules being contained in the unit of
volume. But on the hypothesis that there is the same number of molecules
in the same volume of any gas, the specific gravities of gases can be,
and are, identified with their molecular weights, and, on the ground of
the hypothesis again, the unit of the numbers which enter into every
chemical reaction and constitute the molecular weight, is stipulated to
be that contained in two volumes.
The impossibility of the correctness of the hypothesis is now revealed
by the fact just demonstrated, that in the case of nitrogen the specific
gravity does not coincide with the molecular weight. If equal volumes
contain the same number of molecules, the specific gravities and the
molecular weights must be the same; and if the specific gravities and
molecular weights are not the same, equal volumes cannot contain the
same number of molecules. The assumed molecular weight of nitrogen is
twice as great as the specific gravity, but the molecular weight and
the specific gravity of cyanogen are identical; the number of molecules
contained in one volume of cyanogen must, therefore, necessarily be
twice as great as the number contained in one of nitrogen, and this is
fully and completely borne out by the chemical facts.
In saying that when cyanogen combines with chlorine there is naturally
no condensation, Mr. Greene has no idea that this natural law is fatal
to his artificial law of Avogadro and Ampere; "for," continues he, "the
theory is fulfilled by the actual reaction." It is not. The theory
requires two vols. of cyanogen and two vols. of chlorine, that is, the
unit of numbers, to enter into reaction and to produce two vols. of
the compound. But they produce four vols., and the non-condensation is
therefore in opposition to the theory. It is true beyond doubt that the
molecular weight of cyanogen chloride is contained in two volumes, in
spite of the hypothesis, not on the ground of it; two vols. + two vols.,
producing four vols.; two vols. could, theoretically, contain only half
the unit of numbers, and there seems to be no escape from the following
general conclusions:
1. Two vols. of CNCl, representing the unit of numbers, the constituent
weights, C=12, N=14, Cl=35.5, must each, likewise, represent the same
number; the molecular weight is, therefore, contained in one vol. of N
or Cl, but in two of CNCl and equal numbers are not contained in equal
volumes.
2. The weights N=14, Cl=35.5 occupy in the free state one volume, but
in the combination, CNCl, two volumes; their specific gravity is,
therefore, by chemical action reduced to one half. The fact thus
elicited of the variability and variation of the specific gravity is of
fundamental importance and involves the irrelevancy of the mathematical
demonstration of the hypothesis. In this demonstration the specific
gravity is assumed to be constant, and this assumption not holding good,
and the number of molecules in unit of volume being reduced to one half
when the specific gravity is reduced to the same extent by chemical
action, it is obvious that the mathematical proof must fail. Mr. Greene
states that I have proceeded to demolish C. Clerk Maxwell's conclusion
from mathematical reasoning. This is incorrect; I have found no fault
with the conclusion of the celebrated mathematician, and consider his
reasoning unimpeachable. I am also of opinion that he is entitled to
great credit and respect for the prominent part he has taken in the
development of the kinetic theory, and further think that it was for
the chemists to produce the fact of the variability of the specific
gravities, which they would probably not have failed to do but for the
prevalence of Avogadro's hypothesis, which is virtually the assertion of
the constancy of the specific gravities.
3. The unit of numbers being represented by Cl=35.5, it is likewise
represented by H=1, and as the product of the union of the two elements
is HCl, 36.5 = two vols., combination takes place by addition and not by
substitution; consequently are
4. The elementary molecules not compounds of atoms? And the distinction
between atoms and molecules is an artificial one, not justified by the
natural facts.
5. Is the molecular weight not in every instance = two volumes?
These conclusions overthrow all the fundamental assumptions on which the
hypothesis rests, and leave it, in the full meaning of the term, without
support. Though Mr. Greene states that my arguments are based upon
entirely erroneous premises, he has not even attempted to invalidate a
single one of my premises.
As he considers the non-condensation to be natural in the case of
cyanogen and chlorine, the condensation of two vols. of HCl + two vols.
of H_3N to two vols. of NH_4Cl ought to appear to him unnatural. He,
however, contends for it, and tries, on this solitary occasion, to
strengthen his opinion by authority, though the proof, if it could be
given, that ammonium chloride at the temperature of volatilization is
decomposed into its two constituents, would be insufficient to uphold
the theory.
The ground on which Mr. Greene assumes a partial decomposition at 350 deg.
C. is the slight excess of the observed density (14.43) over that
corresponding to four vols. (13.375). There is, however, a similar
slight excess in the case of the vapor of ammonium cyanide, the same
values being respectively 11.4 and 11; and as this compound is volatile
at 100 deg. C and, at the same time, is capable to exist at a very high
temperature, being formed by the union of carbon with ammonia, nobody
has ever, as far as I am aware, maintained that it is completely or
partially decomposed at volatilization. The excess of weight not being
due, therefore, to such cause in this case, it cannot be due to it in
the other.
The question being whether the molecular weight of ammonium chloride
is two vols. or four vols., an idea of the magnitude of the assumed
decomposition is conveyed by the proportion of the volume of the
decomposed salt to the volume of the non-decomposed, and Mr. Greene's
quotation of the percentage of weight is irrelevant and misleading, and
his number not even correct. A mixture containing
1.055 vols. of spec. gr. 26.75 = 28.22 and
12.32 " " " " 13.375 = 164.78
------ ------
13.375 " 193
has the spec. gr. 193 / 13.375 = 14.43. The proportion in one vol. of
the undecomposed to the decomposed salt is, therefore, as 1 to 11.68 and
the percentage of volume of the former 0.0789, and that of weight 28.22
/ 193 = 0.146, and not 0.16.
It is not easy to imagine why a small fraction of the heavy molecules
should be volatilized undecomposed, the temperature being sufficient
to decompose the great bulk. Marignac assumes, indeed, partial
decomposition, but the difficulties which he encountered in making the
experiments, on the results of which his opinion rests, were so great
that he himself accords to the numbers obtained by him only the value of
a rough approximation.
The heat absorbed in volatilization will comprise the heat of
combination as well as of aggregation, if decomposition takes place, and
will therefore be the same as that set free at combination. Favre and
Silbermann found this to be 743.5 at ordinary temperature, from which
Marignac concludes that it would be 715 for the temperature 350 deg.; he
found as the heat of volatilization 706, but considers the probable
exact value to be between 617 and 818.[1]
[Footnote 1: See _Comptes Rendus_, t. lxvii., p. 877.]
An uncertainty within so wide a range does not justify the confidence
of Mr. Greene which he expresses in these words: "It is, therefore,
extremely probable that ammonium chloride is almost entirely
dissociated, even at the temperature of volatilization." By Boettinger's
apparatus a decomposition may possibly have been demonstrated, but it
remains to be seen whether it is not due to some special cause.
When Mr. Greene says that the relations between the physical properties
of solids and liquids and their molecular composition can in no
manner affect the laws of gases, nobody is likely to dissent; but the
conclusion that their discussion is foreign to the question of the
number of molecules in unit of volume does by no means follow. If the
specific gravity of a solid or the weight of unit of volume represents
a certain number of molecules, and is found to occupy two volumes in a
compound of the solid with another solid, the number of molecules in one
volume is reduced to one half. This I have shown to be the case in a
number of compounds, and the decrease of the specific gravity with
increase of the complexity of composition appears to be a general law,
as may be concluded from the very low specific gravity of the most
highly organized compounds, for instance the fatty bodies, the molecules
of which, being composed of very many constituents, are of heavy weight;
and likewise the compounds which occur in combination with water and
without it, the simpler compound having invariably a greater specific
gravity than the one combined with water; for instance:
BaH_2O_2 sp. gr. 4.495
" " + 8H_2O " 1.656
S_2H_2O_2 " 3.625
" " + 8H_2O " 1.396
FeSO_4 " 3.138
" + 7H_2O " 1.857
and so in every other case. This is now a recurrence of what takes
place in gases, and proves the fallacy of the hypothesis; for if these
compounds could be volatilized the vapor densities would necessarily
vary in the inverse proportion of the degree of composition.
The reproach that Berthelot has been endeavoring for nearly a quarter of
a century to hold back the progress of scientific chemistry, is a great
and unjustifiable misrepresentation of the distinguished chemist
and member of the Institute of France, who has done so much for
thermo-chemistry, and the more unfortunate as it seems to serve only the
purpose of a prelude to the following sentences: "But Mr. Vogel cannot
claim, as can Mr. Berthelot, any real work or experiment, however
roughly performed, suggested by the desire to prove the truth of his
own views. Let him not, then, bring forth old and long since explained
discrepancies, ... but when he will have discovered new or overlooked
facts ... chemists will gladly listen." ... Mr. Greene is here no longer
occupied to investigate whether what I have said concerning Avogadro's
hypothesis is true or false, but with myself he has become personal, and
in noticing his remarks my sole object is to contend against an error
which is much prevalent. If, according to Mr. Greene, the real work of
science consists in experimenting, and conclusions unsupported by our
own experiments have no value, it does not appear for what purpose he
has published his answer to my paper; an experiment of his, settling
Marignac's uncertain results, would have justified the reliance he
places on them. The ground he takes is utterly untenable. Experiments
are necessary to establish facts; without them there could be no
science, and the highest credit is due to those who perform successfully
difficult or costly experiments. Experimenting is, however, not the
aim and object of science, but the means to arrive at the truth; and
discoveries derived from accumulated and generally accepted facts are
not the less valuable on account of not having been derived from new and
special experiment.
It is, further, far from true that the real work of science consists
in experimenting; mental work is not less required, and the greatest
results have not been obtained by experimenters, but by the mental labor
of those who have, from the study of established facts, arrived at
conclusions which the experimenters had failed to draw. This is
naturally so, because a great generalization must explain all the facts
involved, and can be derived only from their study; but the attention
of the experimenter is necessarily absorbed by the special work he
undertakes. I refer to the three greatest events in science: the
discovery of the Copernican system, the three laws of Kepler, and
Newton's law of gravitation, none of which is due to direct and special
experimentation. Copernicus was an astronomer, but the discovery of his
system is due chiefly to his study of the complications of the Ptolemaic
system. Kepler is a memorable witness of what can be accomplished by
skillful and persistent mental labor. "His discoveries were secrets
extorted from nature by the most profound and laborious research." The
discovery of his third law is said to have occupied him seventeen years.
Newton's great discovery is likewise the result of mental labor; he was
enabled to accomplish it by means of the laws of Kepler, the laws of
falling bodies established by Galileo, and Picard's exact measurement of
a degree of a meridian.
If, then, mental work is as indispensable as experimental, it is not
less true that there are men more specially fitted for the one, others
for the other, and the best interests of science will be served when
experiments are made by those specially adapted, skillful, and favorably
situated, and the possibly greatest number of men, able and willing to
do mental work, engage in extracting from the accumulated treasures of
experimental science all the results which they are capable to yield.
Any truth discovered by this means is clear gain, and saves the waste
of time, labor, and money spent in unnecessary experiment. Mr. Greene's
zeal for experiment and depreciation of mental work would be in order,
if ways and means were to be found to render the advancement of science
as difficult and slow as possible; they are decidedly not in the
interest of science, and can not have been inspired by a desire for its
promotion.
As the evidence of the specific heats of the fallacy of Avogadro's
hypothesis involves lengthy explanations, the subject is reserved for
another paper.
San Francisco, Cal., May, 1881.
E. VOGEL.
* * * * *
DYEING REDS WITH ARTIFICIAL ALIZARIN.
By M. MAURICE PRUD'HOMME.
Since several years, the methods of madder dyeing have undergone a
complete revolution, the origin of which we will seek to point out. When
artificial alizarin, thanks to the beautiful researches of Graebe and
Liebermann, made its industrial appearance in 1869, it was soon found
that the commercial product, though yielding beautiful purples, was
incapable of producing brilliant reds (C. Koechlin). While admitting
that the new product was identical with the alizarin extracted from
madder, we were led to conclude that in order to produce fine Turkey
reds, the coloring matters which accompany alizarin must play an
important part. This was the idea propounded by Kuhlmann as far back as
1828 (_Soc. Ind. de Mulhouse_, 49, p. 86). According to the researches
of MM. Schuetzenberger and Schiffert, the coloring matters of madder
are alizarin, purpurin, pseudopurpurin, purpuroxanthin, and an orange
matter, which M. Rosenstiehl considers identical with hydrated purpurin.
Subsequently, there have been added to the list an orange body,
purpuroxantho-carbonic acid of Schunck and Roemer, identical with the
munjistin found by Stenhouse in the madder of India. It was known
that purpuroxanthin does not dye; that pseudopurpurin is very easily
transformed into purpurin, and the uncertainty which was felt concerning
hydrated purpurin left room merely for the hypothesis that Turkey-red
is obtained by the concurrent action of alizarin and purpurin. In the
meantime, the manufacture of artificial alizarin became extended, and a
compound was sold as "alizarin for reds." It is now known, thanks to the
researches of Perkin, Schunck, Roemer, Graebe, and Liebermann, that in
the manufacture of artificial alizarin there are produced three distinct
coloring matters--alizarin, iso or anthrapurpurin, and flavopurpurin,
the two latter being isomers of purpurin. We may remark that purpurin
has not been obtained by direct synthesis. M. de Lalande has produced
it by the oxidation of alizarin. Alizarin is derived from
monosulphanthraquinonic acid, on melting with the hydrate of potassa or
soda. It is a dioxyanthraquinone.
Anthrapurpurin and flavopurpurin are obtained from two isomeric
disulphanthraquinonic acids, improperly named isoanthraflavic and
anthraflavic acids, which are converted into anthrapurpurin and
flavopurpurin by a more profound action of potassa. These two bodies are
trioxyanthraquinones.
We call to mind that alizarin dyes reds of a violet tone, free from
yellow; roses with a blue cast and beautiful purples. Anthrapurpurin and
flavopurpurin differ little from each other, though the shades dyed
with the latter are more yellow. The reds produced with these coloring
matters have a very bright yellowish reflection, but the roses are too
yellow and the purples incline to a dull gray.
Experience with the madder colors shows that a mixture of alizarin and
purpurin yields the most beautiful roses in the steam style, but it is
not the same in dyeing, where the roses got with fleur de garance have
never been equaled.
"Alizarins for reds" all contain more or less of alizarin properly
so-called, from 1 to 10 per cent., along with anthrapurpurin and
flavopurpurin. This proportion does not affect the tone of the reds
obtained further than by preventing them by having too yellow a tone.
The first use of the alizarins for reds was for application of styles,
that is colors containing at once the mordant and the coloring matter
and fixed upon the cloth by the action of steam. Good steam-reds were
easily obtained by using receipts originally designed for extracts of
madder (mixtures of alizarin and purpurin). On the other hand, the first
attempts at dyeing red grounds and red pieces were not successful. The
custom of dyeing up to a brown with fleur and then lightening the shade
by a succession of soapings and cleanings had much to do with this
failure. Goods, mordanted with alumina and dyed with alizarin for reds
up to saturation, never reach the brown tone given by fleur or garancin.
This tone is due in great part to the presence of fawn colored matters,
which the cleanings and soapings served to destroy or remove. The same
operations have also another end--to transform the purpurin into its
hydrate, which is brighter and more solid. The shade, in a word, loses
in depth and gains in brightness. With alizarins for reds, the case is
quite different; they contain no impurities to remove and no bodies
which may gain brightness in consequence of chemical changes under the
influence of the clearings and soapings. These have only one result, in
addition to the formation of a lake of fatty acid, that is to make the
shades lose in intensity. The method of subjecting reds got up with
alizarin to the same treatment as madder-reds was faulty.
There appeared next a method of dyeing bases upon different
principles. The work of M. Schuetzenberger (1864) speaks of the use of
sulpho-conjugated fatty acids for the fixation of aniline colors. In
England, for a number of years, dyed-reds had been padded in soap-baths
and afterwards steamed to brighten the red. In 1867, Braun and Cordier,
of Rouen, exhibited Turkey reds dyed in five days. The pieces were
passed through aluminate of soda at 18 deg. B., then through ammonium
chloride, washed, dyed with garancin, taken through an oil-bath, dried
and steamed for an hour, and were finally cleared in the ordinary manner
for Turkey-reds. The oil-bath was prepared by treating olive-oil with
nitric acid. This preparation, invented by Hirn, was applied since 1846
by Braun (Braun and Cordier). Since 1849, Gros, Roman, and Marozeau,
of Wesserling, printed fine furniture styles by block upon pieces
previously taken through sulpholeic acid. When the pieces were steamed
and washed the reds and roses were superior to the old dyed reds and
roses produced at the cost of many sourings and soapings. Certain makers
of aniline colors sold mixtures ready prepared for printing which were
known to contain sulpholeic acids. There was thus an idea in the air
that sulpholeic acid, under the influence of steam, formed brilliant and
solid lakes with coloring matters. These facts detract in nothing from
the merit of M. Horace Koechlin, who combined these scattered data
into a true discovery. The original process may be summed up under the
following heads: Printing or padding with an aluminous mordant, which is
fixed and cleaned in the usual manner; dyeing in alizarin for reds with
addition of calcium acetate; padding in sulpholeic acid and drying;
steaming and soaping. The process was next introduced into England,
whence it returned with the following modifications; in place of
olive-oil or oleic acid, castor oil was used, as cheaper, and the number
of operations was reduced. Castor oil, modified by sulphuric acid, can
be introduced at once into the dye-beck, so that the fixation of the
coloring matter as the lake of a fatty acid is effected in a single
operation. The dyeing was then followed by steaming and soaping.
For red on white grounds and for red grounds, a mordant of red liquor at
5 deg. to 6 deg. B. is printed on, with a little salt of tin or nitro-muriate of
tin. It is fixed by oxidation at 30 deg. to 35 deg. C., and dunged with cow-dung
and chalk. The pieces are then dyed with 1 part alizarin for reds at 10
per cent., 1/4 to 1/2 oil for reds (containing 50 per cent.), 1-6th part
acetate of lime at 15 deg. B., giving an hour at 70 deg. and half an hour at the
same heat. Wash, pad in oil (50 to 100 grms. per liter of water), dry on
the drum, or better, in the hot flue, and steam for three-quarters to an
hour and a half. The padding in oil is needless, if sufficient oil has
been used in dyeing, and the pieces may be at once dried and steamed.
Wash and soap for three-quarters of an hour at 60 deg.. Give a second
soaping if necessary. If there is no fear of soiling the whites, dye at
a boil for the last half-hour, which is in part equal to steaming.
Red pieces and yarns may be dyed by the process just given for red
grounds; or, prepare in neutral red oil, in the proportion of 150 grms.
per liter of water for pieces and 15 kilos for 100 kilos of yarns. For
pieces, pad with an ordinary machine with rollers covered with
calico. Dry the pieces in the drum, and the yarn in the stove. Steam
three-quarters of an hour at 11/2 atmosphere. Mordant in pyrolignite of
alumina at 10 deg. B., and wash thoroughly. Dye for an hour at 70 deg., and half
an hour longer at the same heat, using for 100 kilos of cloth or yarn 20
kilos alizarin at 10 per cent., 10 kilos acetate of lime at 18 deg. B., and
5 kilos sulpholeic acid. Steam for an hour. Soap for a longer or shorter
time, with or without the addition of soda crystals. There may be added
to the aluminous mordant a little salt of tin to raise the tone. Lastly,
aluminate of soda may be used as a mordant in place of red liquor or
sulphate of alumina.
Certain firms employ a so-called continuous process. The pieces are
passed into a cistern 6 meters long and fitted with rollers. This
dye-bath contains, from 3 to 5 grms. of alizarin per liter of water, and
is heated to 98 deg.. The pieces take 5 minutes to traverse this cistern,
and, owing to the high temperature and the concentration of the dye
liquor, they come out perfectly dyed. Two pieces may even be passed
through at once, one above the other. As the dye-bath becomes exhausted,
it must be recruited from time to time with fresh quantities of
alizarin. The great advantage of this method is that it economizes not
merely time but coloring matter.
The quantity of acetate of lime to be employed in dyeing varies with the
composition of the mordant and with that of the water. Schlumberger has
shown that Turkey-red contains 4 molecules of alumina to 3 of lime.
Rosenstiehl has shown that alumina mordants are properly saturated if
two equivalents of lime are used for each equivalent of alizarin, if the
dyeing is done without oil. These figures require to be modified when
the oil is put into the dye beck, as it precipitates the lime. Acetate
of lime at 15 deg. B., obtained by saturating acetic acid with chalk and
adding a slight excess of acetic acid, contains about 1/4 mol. acetate of
lime.--_Bulletin de la Societe Chimique de Paris._
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