1858, many discoveries were made which helped toward the final
consummation. Even earlier than this the researches of Graham upon
the phosphoric acids had familiarized chemists with the idea that
different substances might have very different combining powers, and
other polybasic acids were found to exist among organic compounds.
The discovery by Wurtz, in 1849, that the hydrogen of ammonia was
replaceable by organic radicles, forming the compound ammonias or
amines, was a logical extension of the theory of substitutions; and
the recognition at about the same time, by Hofmann, of ammonia as a
distinct type upon which many other substances could be modeled, was
another long step forward. In 1851 Williamson argued that nearly all
inorganic and many organic molecules could be represented as analogous
in structure to water, and a year later, as a result of his researches
upon the organo-metallic bodies--zinc ethyl, tin ethyl, etc.--Frankland
expressed the belief that every elementary atom has a definite
combining power which limits the number of other atoms capable of
direct union with it. This was the theory of valence in its first and
simplest form, undeveloped to its consequences, but unmistakably clear.
To carbon compounds in general it was yet to be applied.
In 1858 the work of Cannizzaro appeared, and a general revision of
chemical formulæ became necessary. The advanced views which a few
chemists had held began to find a more general acceptance, and the
significance of the change was gradually realized. In the same year
Kekulé showed that the atom of carbon had a combining capacity of
four, and furthermore that in many organic compounds the carbon atoms
were in part united with each other, and even linked, as it were, into
chains. Still later, studying benzene, he found that its six carbon
atoms were best regarded as joined together in the form of a closed
ring, and with this conception the idea of chemical structure received
at last a definite form. These linkages of atoms, these rings and
their derivatives, could all be represented graphically to the eye,
in accordance with the combining power of the several elements, and
so the structural formulæ of modern chemistry came into vogue. Types,
substitutions, compound radicles, were all covered by and included in
the new generalization, and each of the older theories was seen to be
but an expression of special cases, rather than of any general law. No
truth was set aside, but all were co-ordinated.
To the non-chemical reader the foregoing passages may seem vague
and abstruse, but in an essay of this scope greater elaboration is
inadmissible. It is clear, however, that each forward step has been a
logical development of the atomic theory, which, as we shall see later,
does not end even here.
Thus, then, the chemical formulæ and atomic weights of Berzelius grew
by slow degrees into the modern system, with its representations of
structure and atomic linking. The internal architecture of the molecule
was now revealed not to the imagination only, but to the eye of reason,
and, speculative as the new conceptions may seem at first, they have
led to astonishing practical consequences. The new formulæ at once
indicated lines of research, and with their aid synthetic chemistry
was greatly stimulated. True, many syntheses of organic compounds
had already been made, but progress became more rapid and the work
of discovery was systematized to a wonderful degree. In 1856 Perkin
discovered the first of the coal-tar dyes, creating a new industry
which has been assisted beyond measure by the structural symbols that
came into use only a few years later. In 1868 alizarin, the coloring
principle of madder, was made artificially from the hydrocarbon
anthracene; a host of other colors, a veritable chemical rainbow,
have been discovered; the synthesis of indigo has been effected; and
within twenty years we have seen medicine enriched by a great variety
of drugs, all prepared by purely chemical processes from the former
waste material--coal tar. To most of this work, at least since 1865,
Kekulé’s conception of the benzene ring has been the guiding clew,
and it is certain that without the theory the practice would have
advanced much more slowly. Out of research for its own sake has come
an enrichment of the world, which in any previous age would have been
inconceivable.
The atomic theory, while replacing speculation in one sense, stimulated
it in another. The human mind is always striving to get back of the
known, to see what lies beyond the limits of visibility, and the
conception of an element with its atomic weight opened up a field for
the exercise of the imagination. What is an element ultimately? was
an early question to ask. Are the elements really diverse, or do they
manifest but one fundamental kind of matter? To such queries the atomic
weights offered a promising line for investigation, and more than one
mind began traveling along it. In 1815 Prout put forth the supposition
that all atomic weights were even multiples of that assigned to
hydrogen, and over this hypothesis a long warfare has raged. To-day
it is practically abandoned by chemists, but the controversy which it
provoked led to some of the most accurate investigations in the history
of science, and so served to give precision to our knowledge. Without
the instigation of Prout’s hypothesis, which hinted at hydrogen as
the ultimate form of matter, we might have been content with inferior
determinations of atomic weight, and chemistry, as an exact science,
would have suffered.
In due time, however, it was perceived that the elements could
be arranged in groups, the members of each group having similar
properties and forming similar compounds. Serial relations, analogous
to those discovered among organic compounds, became manifest, and
much thought was expended in seeking to trace out their meaning. The
classification of the elements was more and more seen to be important,
and regularities came to light which at first were unsuspected. Still,
no general law, no one guiding principle, could be found so long as the
old system of weights and formulæ was retained in common usage.
The adoption of Cannizzaro’s atomic weights and the establishment of
the theory of valence made possible a new attack upon the problem of
classification. In 1864 Newlands arranged the elements in the order of
their atomic weights, and showed that at regular intervals there was a
periodic recurrence of certain characteristics. This observation, which
foreshadowed the periodic law, was received with indifference and, to
some extent, with ridicule, but the path had been found which soon led
to a great discovery. In 1869 Mendelejeff published his celebrated
memoir, and the periodic law took its place as a distinct addition to
science. Almost simultaneously Lothar Meyer announced similar views,
but independently, and controversy soon arose as to the relative merits
of the two philosophers. With that controversy we have nothing to do,
but the law itself deserves our fuller attention.
According to the periodic law, all the properties of the elements are
periodic functions of their atomic weights, varying from substance
to substance in a perfectly regular manner. The elements thus fall
into periods, or octaves, as Newlands called them, of a very striking
character. If, for example, we start with univalent lithium, the next
higher element has a valence of two, the next of three, and then comes
carbon, whose atom is quadrivalent. Following carbon, the combining
power of successive elements decreases until we reach sodium, in which
something like the properties of lithium recur. Above sodium the same
rise goes on to the fourth element higher, silicon, which resembles
carbon, and then follows the regular step-by-step falling away, to end
with chlorine, the last member of the second period. This periodic
rising and falling is characteristic of all the elements, and they were
so tabulated by Mendelejeff as to be perfectly clear, with a clearness
which is not to be given by words. In Mendelejeff’s table certain gaps
appeared, which he ascribed to the existence of undiscovered metals.
For three of these he predicted the properties, starting out from
the properties of their neighbors. This was a rash thing to do, but
the venture has been fully vindicated. In 1875 Lecoq de Boisbandram
discovered gallium, which filled one of the gaps; scandium and
germanium filled the other two later. The predictions of Mendelejeff
were fulfilled; atomic weight, specific gravity, fusibility, the
character of the compounds to be formed, were all foreseen for each
of the three new elements; and, so far as experiment has yet gone,
his anticipations have been perfectly realized. Every good theory is
prophetic; but few generalizations have been so strikingly verified
in this respect as has the periodic law. In spite of some outstanding
difficulties, yet to be explained, the law has served to great
advantage in the classification of the elements, and it has had much to
do with the late revival of inorganic chemistry. The latter branch of
science, long comparatively neglected, has now gained new interest, and
for it, in the near future, a great growth can be prophesied.
The immediate effect of the periodic law was to prove that the
elements are connected with one another by general relations, and so
to stimulate the belief in their possibly common origin. This view has
many upholders, although it is also strongly opposed, but the weight
of argument seems to be in its favor. On philosophic grounds it is at
least more probable than the opposite opinion, which can not account
in any way for the regularities which have been observed. From another
source, partly physical and partly chemical, the theory of the unity
of matter has received strong support, and this statement brings us
to another of the greatest discoveries made during the nineteenth
century--that of the spectroscope and spectrum analysis.
It was in 1860 that Kirchhoff and Bunsen added this new weapon to
the arsenal of scientific research. The spectroscope itself, as
an instrument, was an invention in the department of optics, but
its applications to chemistry were among the most obvious and the
most startling of its achievements. With its aid new elements were
discovered--rubidium, cæsium, thallium, indium, and gallium; in many
lines of investigation it found immediate use; but, more than all, it
made possible the analysis of the heavenly bodies, and proved that the
same kinds of matter exist throughout the visible universe. Before the
day of the spectroscope all speculation upon the chemistry of the stars
was in vain; with its advent the material unity of planets, suns, and
nebulæ was made clear. To the astronomer, a new eye was given; to the
chemist, a new laboratory. Three sciences were brought to a single
focus, and each one gained in power thereby.
In its application to what may be called chemical astronomy, one
achievement of the spectroscope was particularly notable--namely, the
rehabilitation of the nebular hypothesis. When the gigantic telescope
of Lord Rosse had resolved some nebulæ into clusters of stars, it
was thought that all other nebulæ might be of the same character;
the visible basis of the hypothesis was gone. But the spectroscope
soon found among these celestial objects some which were truly clouds
of incandescent gas, and so the nebular hypothesis received a new
standing, becoming stronger than ever before. One point, however,
was strange: these gaseous clouds were of the simplest composition;
hydrogen and nitrogen were their chief constituents; how, then, could a
world like ours originate from them?
Further investigation, to which Huggins and Secchi were the chief
contributors, showed, however, that from nebula to planet there is
a regular, progressive order of chemical complexity. The nebulæ are
simple; in the hotter stars a few more elements appear; more still can
be detected in colored stars and the sun; but the planets, represented
by our earth, are most complex of all. So far the facts; the scientific
imagination now comes into play. If suns and planets were derived
by a process of condensation from such nebulæ as exist to-day,
perhaps the process of evolution was attended by an evolution of the
chemical elements themselves. Upon that supposition the facts become
intelligible; without it the evidence is not easily co-ordinated. This
hint, together with the suggestions offered by the periodic law, has
made chemists more ready to consider the probable unity of matter,
even though actual proof for or against the conception has not yet
been attained. That the chemical elements are absolute and final few
thinkers of to-day believe; the drift of opinion is mainly in one
direction, but no element has yet been decomposed or transmuted into
another. Some mathematical relations have been found connecting the
atomic weights of certain elements with the wave lengths of their
spectral lines, and this field of investigation is a promising one for
the future. That the atomic weights are connected hardly admits of
doubt; to the mass of the atom its rate of vibration must be related;
to that vibration the lines in the spectrum are due. The clews are
obvious, and it will be strange if they do not lead to important
discoveries ere long.
[_To be concluded._]
THE SCIENCE OF ART FORM.
BY D. CADY EATON.
Taste is so free and so subjective, so largely a matter of personal
feeling, that any selection or limitation of attractive objects
would be met by plausible objection. Every honest and unprejudiced
investigator must, however, admit nowadays that his individual taste
may be informed and purified, and that he is under obligations to
be ever ready to explain and to justify it. The day for the mere
proclaiming of preference has passed. The proclamation must be
accompanied by explanations which will satisfy others, if they do not
convince them, and which will be clear to one’s own understanding. The
authoritative explanation, “I like this, I dislike that,” will no more
pass current nor carry weight. Science has sufficiently studied the
sentiments and emotions to know that they, too, are subject to laws
which must be acknowledged and obeyed. Excitations for which there is
no reasonable accounting, no justifiable source, must be relegated
to the domain of folly. The reason for everything that appertains to
thought and emotion, if not apparent, must be exposed and presented.
Artists must explain their works to vulgar understanding. Writers must
make their criticisms plain to the humble intellect. The age in which
we live takes nothing for granted, accepts no man’s _ipse dixit_, hates
shams, is intolerant of secrecy, hypocrisy, and fraud.
I propose in this article, by contrasting good and bad examples, to put
before readers a few of the simplest elements of decoration. You can
hardly fail to note the differences, and when once the eye has acquired
the habit of discriminating there is no reason why there should not
follow a growth in perception which will result in delightful and
augmenting artistic enjoyment. No attempt is to be made to develop a
system, nor, of course, to cover the whole ground of the subject. The
object is simply to start perceptions in the right direction.
Almost all the ideas and the illustrations of this article are taken
from a little work by Henri Mayeux, called _La Composition Décorative_.
Henri Mayeux is Professor of Decorative Art in the École des Beaux-Arts
in Paris. His work is one of the series of the _Bibliothèque de
l’Enseignement des Beaux-Arts_, a series which should be among the very
first works to be found in the library of every student of art.
[Illustration: FIG. 1.]
The very first of Mayeux’s illustrations (Fig. 1) introduces the style
of the teaching of the volume and of this article. Let me translate
his accompanying description: “Here are two recipients of the same
height, made of the same material, and with about equal care. Each has
two handles and is decorated by the same number of fillets. The one
marked _A_ is the work of an ordinary potter, without artistic instinct
or education. The other, _B_, is a Greek vase of fine and delicate
taste. No one can fail to appreciate the superiority of _B_ to _A_. The
purity of its profile, the graceful manner in which the handles are
attached, the calculated division of the fillets, establish at once a
considerable difference of artistic value between the two objects.” If
Mayeux were addressing beginners he might add that one reason why all
jugs and vases are round is that the shape is the easiest to make. The
potter’s wheel must have been one of the very earliest inventions of
semi-civilized races. Besides, as a drop of water is globular, it seems
appropriate that liquids should be contained in round receptacles. A
square jug would not only seem inappropriate, but it would be ugly
and perhaps difficult to handle. Notice in _B_ how much better the
different parts are distinguished: the neck from the body of the
vessel, and the body of the vessel from the foot. Two fillets are also
very appropriately put where the vessel is largest, and where they seem
to convey a sense of increased strength exactly where the pressure is
greatest. You will find all the way through the study of ornament that
utility, or use, is a fundamental principle which can not be violated
without impairing beauty.
Before presenting objects for comparison it may be well to pass in
review the elements which compose all objects. Decoration is the
application of ornament to form. It therefore presupposes knowledge
of both form and ornament, for form must be understood by itself, and
ornament by itself, before the proper ornament may be selected for the
given form. The elements of form are length, breadth, and thickness. A
mathematical point is conceived to have no dimensions, a mathematical
line but one, and a mathematical plane but two. But in actuality there
is no tangible object without the third dimension--thickness. Still,
where two dimensions are very much more prominent than the third--as,
for instance, in a plaque, in the side of a room, in a single
elevation of a building, or whenever merely the surface of an object
is viewed--the third dimension may be left out of consideration. Lines
and the surfaces they bound--that is, length and breadth--are the two
elements of form which play the chief part in decoration.
[Illustration: FIG. 2.]
[Illustration: FIG. 3.]
If the two vases which are represented in the view by vertical and
horizontal, straight and curved lines, were actually before us you
would have difficulty in finding any vertical lines, and the horizontal
lines would turn out to be circles. The lines in the view mark the
apparent terminations of the surfaces. For purposes of study, however,
you must regard objects of three dimensions as bounded by lines, just
as they appear in photographs, drawings, or other flat representations,
geometric or perspective. In regarding objects from the point of view
of decoration there is still another element to be considered; that is,
the element of material, the substance of which objects consist, for it
is evident that the ornament which would be appropriate to wood, for
instance, might not be appropriate to metal or to stone. The element of
material is of great importance in practical decoration, but of less
importance in theoretical decoration. Lines and surfaces are therefore
the two chief elements of decoration to be considered at present.
Color, being an element of an entirely independent nature, will not be
considered at all.
First, lines. The lines down one side of an object may be called the
profile of the object, while the lines surrounding the object may be
called the contour or outline of the object.
[Illustration: FIG. 4.]
Profiles and outlines are made up of any number of straight and curved
lines connected at any and every variety of angle. The view (Fig. 2)
shows a few possibilities of combination of lines into profiles. The
particular thing to be observed in these profiles is that individual
curves are preceded or followed by curves which curve in the same
direction or in the opposite direction--that is, regarding the curves
as concave or convex from a given side of the profile, sometimes a
concave curve meets a concave curve, sometimes it meets a convex curve.
In these particular profiles the straight lines which unite the curves
are so small and so insignificant that they appear as mere connections.
Where the adjoining curves are homogeneous the connection is called
continuous--_raccords continus_, as Mayeux puts it. When the adjoining
curves are different, the connection is called contrasted--_raccords
contrastés_. In the view all continuous connections are marked _a_; all
contrasted connections are marked _b_. Now follow these lines up and
down slowly and deliberately--not once or twice, but a number of times.
See exactly where the connections occur, and where the connections
are continuous, and where they are contrasted. In these profiles are
shown forth and made evident two of the most important and general laws
not only of ornament, but of all artistic composition: First, that
connected curves of the same kind must run substantially in the same
direction; and, second, that for purposes of strong contrast curves of
different kinds must be joined--that is to say, that where contrasted
connection is desired, the difference in direction must be abruptly
and sharply indicated. In the profiles in the view the various curves
have been continued in dotted lines beyond the profiles, so as to bring
out and make clear these two laws. You see that wherever there is a
_b._ the dotted lines cross at, or nearly at, right angles, and that
wherever there is an _a._ there is no crossing at all of the dotted
lines. The essence of these two laws is of such importance in all
artistic and decorative composition that beginners might well be put
to drawing profiles until the principles involved have been absorbed
and made a part of artistic apprehension. The profiles in the view are
all pleasing, because the laws are observed. Try your hand at drawing
profiles in which the laws are not observed, and you will quickly
perceive the difference. The most beautiful of pure profiles are those
presented by Greek entablatures. The most beautiful of Greek outlines
are those presented by Greek vases. The beauties of Greek sculpture and
of renaissance design belong so strictly to the domain of pure art that
they may not be used for comparison in an article on ornament.
[Illustration: FIG. 5.]
[Illustration: FIG. 6.]
As outlines are composed of profiles, the same laws govern. That
the curved line is the line of beauty stands out most evidently in
the study of antique designs. Vertical lines and horizontal lines
are the lines of support and strength, and must always have proper
consideration; but in pure ornament the office of straight lines seems
to be confined to connecting curves and to emphasizing their contrasts.
[Illustration: FIG. 7.]
The next view (Fig. 3) is to illustrate the progress already made.
On the upper line are the three rough outline sketches for modern
articles, of which the final use and destination are shown on the lower
line. In the sketch to the left the fine effect is produced by a few
curves, of which the connections are boldly and finely contrasted. In
the second sketch an equally pleasing effect is produced by curves, of
which the principal ones are continuously connected, while in the third
sketch there is a pleasing exhibition of both kinds of connections.
The lower line gives you your first notion of the use of ornament in
marking and embellishing the lines of form.
[Illustration: _Contours bátards et indécis_ FIG. 8.]
The next view (Fig. 4) exposes forms in which the above laws are
violated, and by whose ugliness you can not fail to be impressed. On
the top line are objects of which the curves are so weak and undecided
that it would be difficult to state whether the connections are
continuous or contrasted. In the second line is shown how ugly is the
effect when straight lines are substituted for curved lines, and in the
third line is shown how ugly effects may be produced even by curved
lines when not used in obedience to some accepted and apprehended
principle.
[Illustration: FIG. 9.]
There is another presentation of form which is in reality but a
modification of profile, but which, because it looks as if it had
been separately applied, and also because it is separately treated
in books, must be considered by itself. The term “molding” has been
given to variations in surfaces which have both useful and ornamental
uses. Moldings are as old as architecture, and vary with schools of
architecture.
[Illustration: FIG. 10.]