recent organic syntheses may be described simply as a war against agriculture. But there is a limit, which is sometimes not taken into account. We shall ultimately, doubtless, be able to reproduce artificially every organic compound existing in nature. But there is no prospect that we shall be able to make artificially any organism or any part of an organism. Suppose we should be able to form synthetically malic acid, fruit sugar, and cellulose; we should not be in the least nearer to the power of making an apple. Wherever there is not merely peculiar chemical composition, but peculiar tissue, there the scope of chemistry is at an end. Hence, though the formation of starch and gluten may ultimately come within our power, we have no prospect of ever being able artificially to produce a grain of wheat.

Among the chief triumphs of organic synthesis must rank the formation of so-called "saccharine " by Professor Remsen and Dr. Fahlberg. This substance, we must bear in mind, has none of the properties of sugar except sweetness. It does not in any way contribute to nutrition. It has its uses, doubtless, for sweetening the food of invalids to whom sugar would prove injurious, such as diabetic patients. On the other hand, it opens the door to a series of frauds, as a small quantity of it may enable various worthless substances, so long as they are soluble, to be sold as sugar. Its taste, moreover, is not exactly like that of sugar. Bees and wasps turn from it with an angry hum, and even flies will not touch it. But we must remember that the senses of many insects are not only more delicate than our own, but reveal differences which we cannot detect even with our instruments of precision. A bee will not touch beet-root sugar if cane sugar is at hand. It is, however, perfectly possible that chemical science may yet put us in possession of a true artificial sugar.

Other experimentalists have turned their attention to perfumes. The so-called fruit essences, which are supposed to communicate to confectionery and to liqueurs the flavors of pineapples, of the jargonelle pear, and of apples, are open to grave suspicion. It is not proved that their physiological action is identical with that of the fruits whose flavors they simulate. Some of the ptomaïnes and alkaloids extracted from putrid or diseased animal matter, though highly poisonous, possess the

odors of cinnamon, of the rose, or of the syringa. An artificial musk, recently obtained, not only gives off the exact odor of the natural product, but is said to have the same medicinal action. Hence the musk deer may consider itself disestablished.

The synthetic chemists have been most active and most successful in making dyes. Some natural coloring matters, such as turmeric, archil, and safflower, have been nearly superseded. But the two most important dyes, alizarine and indigo, have been not only imitated, but actually made artificially. The history of both is no longer novel, but I may mention that quite lately two chemists, one a Swiss and the other a German, have succeeded in producing artificial indigo at a price which will enable it to compete with the natural product. A recent inventor brings forward a so-called artificial silk. His product, however, is not silk, but merely cotton fiber modified so as to imitate some of the properties of silk. Hence it forms no exception to the rule that we cannot reproduce organic structures.

Attempts have been made, not without success, to form minerals. Artificial ultramarine has long been an article of commerce. The formation of the diamond is said to have been actually effected, but in the opinion of the inventor the process is so difficult and so dangerous, that the diamond-miner and the diamond-merchant need not feel uneasy. The ruby and the sapphire have lately been reproduced in Paris, and, curiously enough, the coloring matter in both is found to be due to one and the same metal-chromium-in different states of combination. Red and blue stones, or an intermediate violet form which might be likened to the rare and beautiful oriental amethyst, have been obtained in one and the same operation, from the same lot of material. The jewels thus produced have so far all been small; large enough to form the pivots of superior watch works, but not large enough to rank as rare and costly ornamental objects.

Passing, in conclusion, to more general considerations, we may note that our conceptions of atoms and molecules, as the component parts of matter, have been extended. Dalton and most of the chemists of the present day conceive of the atom as a body, minute indeed, but not infinitely so; divisible in the imagination of the mathematician, but not capable of being actually

broken up by any means at our command. The conflicting theory of Boscovitch, which was adopted by Faraday, regards atoms as mere mathematical points, centers of forces, or, as we should now say, forms of energy. To compare these two views in detail would be here impracticable, but several advances have been lately made in our insight into the conformation of matter. It has long been considered that the atoms are grouped together in so-called molecules. Each such molecule is composed of a fixed number, generally small, of atoms. These molecules, if they belong to one and the same chemical species, are alike in the number and the kind of atoms of which they are composed. But we find, on analysis, bodies which contain the very same substances in exactly the same proportions; and yet such bodies may differ in their boiling and congealing points, in their colors, in their odors, and in their physiological action. The only way of explaining these differences is by supposing that the atoms in each molecule are arranged differently, and that this modifies the properties of the substance. The arrangement of atoms in the molecules of a compound body is known as its "constitution," which must not be confounded with its composition. The constitutions of compound bodies have until lately been represented by certain formulas, which show the symbols of their elements disposed on a plane surface. It is now found that the mutual relations of such elementary atoms may be shown forth more clearly by supposing them to be disposed on a body of three dimensions. But this is not all. It appears now that the atoms in the molecule are not motionless, but that they are in a state of vibration or rotation-motion, in short, comparable to that of the bodies of the solar system. So minute are the atoms that, in a molecule which is not even visible to our senses, and which might be thought a concrete whole, they may be relatively as far apart as the sun and the planets.

We see thus that in chemistry, though we have gained much truth, though we have acquired the powers of creation and prediction, there are still not mere gaps, but abysses, to be filled up. For this task not one Curtius, but many, will be needed. WILLIAM CROOKES.

THE BERTILLON SYSTEM OF IDENTIFICATION.

men.

IN all ages questions of identity have excited the interest of Is it not at bottom a problem of this sort that forms the basis of the everlasting popular melodrama about lost, exchanged, and recovered children? Actual history is not less rich in facts and stories of this kind. Almost all the French historians, for example, have striven to identify the celebrated prisoner of Louis XIV., known as "The Man with the Iron Mask," not to mention the pretended descendants of J. J. Rousseau and of Louis XIV., who, in the face of all evidence, have succeeded in making some people take their claims seriously.

But it is naturally the world of criminals that has furnished, and yet furnishes, the greatest number of such attempts at deceit. It is not generally known by the honest public how large a number of malefactors have recourse to concealment of identity. We may assert without exaggeration that there is not a single habitual criminal who does not seek to hide his individuality when the circumstances of his arrest permit. The immensity of modern cities and the increasing facility of communication make this course more and more easy. International criminals, such as bank-robbers and pickpockets, traverse two continents, changing their names from country to country. The greater, therefore, becomes the necessity of some methodical system of identification.

It was believed for a short time, thirty years since, that photography was to give the solution of the problem. But the collection of criminal portraits has already attained a size so considerable that it has become physically impossible to discover among them the likeness of an individual who has assumed a false name. It goes for nothing that in the past ten years the Paris police have collected more than 100,000 photographs. Does the reader believe it practicable to compare successively each of these with each one of the 100 individuals who are arrested daily

in Paris? When this was attempted in the case of a criminal particularly easy to identify, the search demanded more than a week of application, not to speak of the errors and oversights which a task so fatiguing to the eye could not fail to occasion. There was need of a method of elimination analogous to that in use in botany and zoology; that is to say, one based on the characteristic elements of individuality, and not on the station and occupation of the accused, which may be erroneously given.

I may remark, in passing, that the absence of a natural method of classification is a reproach that applies equally to all means of judicial identification with which it has been sought to replace photography. Among these are: 1, impressions of the minute channels that traverse the skin of the thumb, according to a method introduced by Francis Galton, in imitation, it would appear, of one in use in China; 2, plaster casts of the jaw, suggested by certain dentists as a method of identification; 3, the markings on the iris, observed by practically the same method as that proposed by me a dozen years ago; 4, impressions, casts, or photographs of the ear, whose channels and ridges present so many individual varieties that it is impossible to find two human ears that are alike, and such great permanence in the same person that the form remains practically the same from infancy to old age.

It has been said, long since, that it is impossible to find two leaves exactly alike. Nature never repeats herself. Choose any part of the human body, examine it, and compare it carefully with the same part of another person, and differences will appear, more or less numerous, as your examination has been more or less minute. You will find external variations; internal variations in the skeleton, the muscles, the course of the veins and arteries; physiological variations in the gait, the expressions of the countenance, and the organic secretions. The dog who seeks his master in a crowd makes his way through it on a run, his nose to the ground. Homer tells us that after twenty years of absence, Ulysses, disguised as a beggar, was recognized only by his dog, "the faithful Argos, with excellent scent." Here is an element of individuality, and consequently of recognition, that escapes the sense of man completely. But a few words, pronounced in a natural tone and "Edisonized" by a phono