ful nurserymen near York, where he grows not only our royal socalled "flowering fern," the Osmunda regalis, and several foreign

Entrance to Cave for Killarney Fern in Rock-garden.

allied species, but the most beautiful of all this beautiful tribe, the moisture-loving Killarney fern, which clothes the soil of the damp dark woods by the Torc waterfall.

The beauty of these horticultural experiments is that they can be tried on so small a scale, and are thus within the reach of almost every one; yielding a source of pure and healthy enjoyment which few other pursuits will afford. Mr. Robinson almost promises us that his little book shall be the first of a series of similar manuals on different departments of gardening; and we can hardly conceive a greater service than this to a large number of his countrymen, who merely require to be told how to set to work to cultivate this fascinating science.

VII. A RECENT TRIUMPH OF SYNTHETICAL

CHEMISTRY.

It is not often that so legitimate a triumph of synthetical chemistry as the artificial production of a natural substance becomes, at the same time, an important national discovery, the money value of which may be reckoned by millions. Such, without exaggeration, it is not unlikely that the artificial production of Alizarine, the colouring matter of madder, may become.

Madder is the root of a plant belonging to the order of Rubiaces, amongst which are included some valuable plants, such as the cinchona, ipecacuanha, and coffee. The madder plant is the rubia tinctorum. It is estimated that its consumption reaches over 47,000 tons per annum, and this, at 457. per ton, amounts to over 2,000,0007. sterling, one half of which is imported to England, and the payment for which (1,000,0007.) goes out of this country into the pockets of foreign manufacturers. If now the essential constituent for which madder is so valuable, its pure colouring matter, can be economically prepared by chemical means from coal-tar, that amount of money will naturally go into our own pockets—a not unworthy reward for chemical ingenuity.

The value of madder in dyeing and calico printing depends upon the many different colours which can be dyed by its means; thus, one mordant (iron) gives purple shades, from the most delicate mauve to black; with another mordant (alumina), red shades are produced, from the palest pink to deep crimson, including the brilliant and well-known Turkey red; and by judicious admixture of these mordants, combinations of all varieties of chocolate-brown are produced. These colours are very permanent, whilst the high price of the raw material to which they are due renders the discovery of a substitute a problem of the highest commercial importance. For these reasons the chemical investigations of madder have been very numerous, the most valuable results having been obtained by our own countryman, Dr. Schunck. This chemist found that the root did not contain a colouring matter ready formed, but there was in it, amongst many other bodies, a crystalline substance, which he named rubianic acid. When the powdered madder is allowed to stand in a moist state, or is gently heated with water in the dyebeck, a peculiar fermentation sets up under the influence of a ferment called erythrozyn, by which the rubianic acid is split up into alizarine and glucose. Besides alizarine, there is another colouring matter obtained from madder, called purpurine; but as all the valuable shades and colours of madder are due to the alizarine, we need only devote attention to the latter substance.

Alizarine is a brilliant scarlet substance, which crystallizes in

prisms, and when exposed to carefully-regulated heat, sublimes, condensing into beautiful tufts of scarlet needles; it is only sparingly soluble in water, but dissolves in spirit, and in alkaline solutions; its tinctorial power is at least thirty-five times as great as that of madder itself. Dr. Schunck was the first to point out that Turkey red, madder pink, and all the finer madder colours, are simply compounds of alizarine and fatty acids with bases, and he has described a process for preparing pure alizarine from cotton which has been dyed Turkey red.

The discovery of the method of preparing alizarine artificially is due to two continental chemists, Messrs. Graebe and Liebermann, and their discovery is the more remarkable, since it has not been effected by any haphazard, rule-of-thumb system of experimentation, but is the result of a scientific investigation on the properties and molecular structure of alizarine, and has been conducted, step by step, in accordance with logical deductions from the known laws of synthetical chemistry. The train of reasoning is too complicated, and requires too profound a knowledge of the laws of modern chemistry, to be given in detail here, but a brief outline of their research will perhaps be of interest.

From an examination of the substances obtained when pure alizarine from madder was submitted to sundry chemical processes, it was ascertained that this principle was connected with the hydrocarbon group containing fourteen atoms of carbon, and by heating it with a body capable of removing oxygen, they obtained from it the hydro-carbon of the group, containing fourteen atoms of carbon and ten of hydrogen. This was seen to be identical with one of the solid crystalline bodies obtained in the distillation of coal, named anthracene; and by a somewhat complicated process they converted this into anthraquinone, then into bibrom-anthraquinone, and lastly, into alizarine; having by this means added four atoms of oxygen to and removed two atoms of hydrogen from the alizarine. The key to the synthetical formation of alizarine having thus been discovered, it was not long before improvements were effected; for when a particular series of chemical reactions have to be performed, a clever chemist can always find different ways of effecting them, as the records of many a celebrated patent case will show. There are now four processes in operation, three of which are patented, whilst one is being worked secretly. All effect the same purpose by somewhat similar means, but by the use of different reagents, and all start from anthracene. Mr. Perkin's patent is now in operation in this country, and his artificial alizarine is in use amongst the Scotch dyers, where it is competing favourably with madder. Besides alizarine, other colouring matters are formed during these synthetical operations; and unless care is taken in the purification, the tones produced by the artificial colouring matter are liable to be somewhat yellowish;

but when pure, there is no doubt as to the identity of the artificial and natural dyes, as they are similar in their absorption spectra, their tinctorial powers, their unalterability under the influence of light, and their solubility.

Whether artificial alizarine will supersede madder to any great extent depends principally on the supply of the raw material, anthracene. Dr. Roscoe says that in an experiment made on a large scale it was found that 100 tons of tar yielded 0.63 ton of anthracene, or 1 ton of anthracene could be obtained from the distillation of about 2000 tons of coal, not reckoning the quantity of anthracene contained in the pitch. But tar distillers have hitherto turned very little attention to this substance, and from some experiments of Mr. Perkin it is probable that some kinds of coal-tar contain considerable quantities of anthracene. Attention being now directed to the subject, all experience tells us that the demand will bring a supply, and already we see signs of this in the advertisement pages of chemical periodicals, where the price of anthracene is regularly quoted along with that of other coal-tar products. Should our anticipations be fulfilled, this discovery, although made by German chemists, cannot fail to be of most benefit to England, the great tar-producing country of the world. Tar distillers will do well to bear this in mind, and examine the influence of various temperatures in distillation, for anthracene is likely to become as important as benzol was a few

years ago.

W. C.

NOTICES OF SCIENTIFIC WORKS.

FORMS OF ANIMAL LIFE.*

TWENTY years ago a number of statutes were passed in the University of Oxford indicative of a commencing change in the educational methods pursued at that venerable institution, of which change the book before us is one of the fruits. The "progressive studies," and prominently among them the study of the natural sciences, were introduced as legitimate objects of pursuit; and the admission thus made that, in the opinion of some, they were at least competent to supplement, if not to supplant, as agents of intellectual discipline, the investigation of the ancient classics, or of the philosophical works of Kant and Hamilton.

Whether science, however, as distinct from literature, be efficient in developing the mental faculties and engendering correct habits of thought, must depend entirely on the method in which it is pursued. It must be obvious to anyone who has had much experience in teaching, that it is quite as easy-and perhaps even easier for a youth to acquire a scientific as a classical pedantry; to be able glibly to talk chemistry, as many boys do their Latin, by employing a confused jumble of words and formulæ, without the slightest appreciation of broad general principles. It is, indeed, quite marvellous how little has been effected in England in some branches of science, even under circumstances that would at first sight appear most favourable, merely through the pursuit of a wrong method. Ask ninety-nine out of a hundred senior medical students what the effect of a section of the phrenic or the sympathetic nerve would be, and they will probably detail certain characteristic changes in the respiration and circulation. Supplement the first question by another requiring the source of their information, and they will at once give the name of the compiler of the physiological text-book most in vogue at the time. Now ask two similar questions concerning the situations of these nerves in the human body, and the replies will be of a very different character. Their directions and relations to contiguous parts will be promply set forth; and in reply to the second query the students will inform you that they have seen the nerves with their own eyes, and dissected them with their own scalpels, and are quite prepared to prove the correctness of their statements by a demonstration of

* Forms of Animal Life: being Outlines of Zoological Classification based upon Anatomical Investigation, and Illustrated by Descriptions of Specimens and of Figures.' By George Rolleston, D.M., F.R.S., Linacre Professor of Anatomy and Physiology in the University of Oxford. Oxford: Clarendon Press.

VOL. VII.

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