FORMATION OF Vinegar by BACTERIA.-E. Wurm has investigated this matter, and his results prove, without doubt, that an active formation of vinegar from alcohol is obtained by means of Myccderma aceti (Bacterium mycodermaCohn), thus supporting Pasteur's view.

ORGANISMS IN BEET SAP.-The bodies known as "frogspawn," which make their appearance after a time in the sap of the beet root, prove, on microscopic examination to be a species of bacterium, called by L. Cienkowski, Ascoccus Bilrothu.

PTYALIN AND DIASTASE.-T. Defresne has found that ptyalin converts starch into sugar, in the presence of impure gastric juice, as rapidly as it does in the mouth. Its action is, however, suspended by pure gastric juice; but on passing into the duodenum the ptyalin again becomes active. Diastase, on the other hand, is completely deprived of its power of converting starch into sugar by hydrochloric acid or by pure gastric juice. (Compt. Řend., 89, 1070.)

ABNORMAL COMPOSITION OF MILK.-According to C. Marchaud (Bied. Centr., 1872, pp, 769-770), the usual composition of human milk is as follows: butter, 36.8; lactose, 71.1; protein, 17; salts, 2.04, and water, 873 parts per thousand. When the amount of butter rises to above 52 parts, the milk is injurious to the child. The quantity of protein, which is much less than in cow's milk, cannot be exceeded without ill effects.

NUTRITIVE VALUE OF GRASS AT VARIOUS STAGES OF GROWTH.-E. von Wolff and others (Bied. Centr., 1879, pp. 736-744) cut grass three times in the early summer, in the years 1874 and 1877; the first cutting took place about the middle of May, the second at the beginning and the third at the end of June. The second cutting appeared to give the best results in the case of animals experimented upon, namely sheep and horses; and, as a rule, it was found that more nitrogenous matter was excreted by the latter than by the former.

ANALYSIS OF TWO ANCIENT SAMPLES OF BUTTER.-G. W. Wigner and A. Church have examined a sample of Irish bog butter, which cannot be traced with any certainty to a particular locality. There is no doubt, however, that it is a perfectly authentic specimen, probably 1000 years old. The following results were obtained: volatile fatty acids, calculated as butyric, 6 per cent; soluble fatty acids, not volatile, 42 per cent; insoluble fixed fatty acids, 99.48 per cent; glycerol, minute traces. The insoluble fatty acids contained 9 per cent. oleic acid, and 91.0 per cent stearic and palmitic acids.

The other sample of butter, which is much older, was taken some time ago from an Egyptian tomb. It dates from about 400 or 600 years before Christ. It was contained in a small alabaster vase, and had apparently been poured in while in a melting state. In appearance, color, smell and taste, it corresponds closely with a sample of slightly rancid butter. Analysis shows that the sample has not undergone any notable decomposition.

CHLORIDE OF Platinum.-Dissolve the metal in hydrochloric acid, 5 parts; and nitric acid 3 parts-a florence flask is convenient for this purpose. When all the metal is dissolved transfer the solution to a porcelain evaporating dish, and apply heat until nearly the whole of the acid is expelled. Dissolved in water or in ether chloride of platinum is useful for imparting to brass articles a steel like appearance.

THE EFFECT OF CARBONIC ACID IN THE AIR UPON CROPS.According to M. Marie-Davy, (Compt. rend. 90, pp. 32-35), an examination of the determinations of the amount of carbonic anhydride in the air, which have been made daily dur ing the last four years at Montsouris, seems to show that the best crops have been produced in those years when the amount of carbonic anhydride has been below the average. The carbonic anhydride varies inversely with clearness of the sky, and is influenced by the oscillations of the great equatorial atmospheric currents.

RESPIRATIVE POWER OF MARSH AND WATER PLANTS.-It is a well-known fact that these plants are able to thrive in media which contain little or no oxygen. They are all very poor in nitrogen, and E. Freyberg has shown by a number of experiments, that this latter property accounts for the former. His investigations prove that the respirative power of plants varies with the amount of nitrogen they consume, and this, taken in conjunction with the fact that water-plants contain large air chambers which do not often need refilling, accounts for their being able to exist in media which contain very little oxygen.

A RAILWAY BREAK, which is instantaneously applied and continuous in its action, and which the inventor proposes to render automatic, is described by M. Hospitalier in La Nature. It is worked by means of two of the secondary batteries of M. Plantè, each of these being charged by three Daniell cells. The action of the apparatus is dependent upon the adhesion of an electro-magnet to the axle of the wheels, by means of which two chains attached to levers carrying friction blocks, are wound upon a drum.

ARTIFICIAL DIAMONDS.—In regard to the successful work of Mr. Hannay, of Glasgow, in producing perfect artificial diamonds, it may be well to bear in mind the similar investigation carried on by Despretz, the noted French chemist. Some authorities allege that the results obtained by Despretz were in advance of those reached by Mr. Hannay, yet the former, at the conclusion of five years of labor, made the frank acknowledgment that he had not found the diamond proper, although he had obtained crystals of pure carbon possessing all the characteristics of the coveted prize.

CYANIDE OF POTASSIUM.-There are many substances which are difficult to procure, whereas the materials of which they arecomposed are within the reach of everybody. To make Cyanide of Potassium, use the following formula:

Reduce the prussiate of potash to a coarse powder, and dry upon an open plate over a slow fire; next dry the carbonate of potash thoroughly, when both substances are to be intimately mixed. Put the mixture in a crucible or deep iron ladle, and place in a clear burnt coke fire. When fusion takes place, stir occasionally with an iron rod. When the mass is thoroughly fused allow it to continue in that state for at least a quarter of an hour. If on dipping the iron rod into the melted mass the compound appears white on cooling, the ladle may be withdrawn from the fire, allowed to rest for a few minutes, when the cyanide which is formed, must be poured in patches on an iron slab or flagstone, care being taken not to allow the dross, which is chiefly iron, to pass out with the clear fused cyanide. The "dross" should be shaken out separately, and when cold washed with water to dissolve out the adherent cyanide, after which the washing water may be filtered and used as a solution of cyanide when required. Keep the cyanide in a wide mouth bottle well corked, and labelled.

VISUAL TELEGRAPHY.

For many years past scientific men have been familiar with the fact, that the reflected images of objects could be reproduced at a distance by the aid of electricity, but recently the matter has been again taken up, and is now being prominently brought before the public under headings of "seeing by telegraph."· The general principle involved may be gathered from the description of the "Diaphote," an instrument introduced by Dr. H. E. Licks of Bethlehem, Penn., "for seeing by telegraph." He calls it by this name from two Greek words, dia, through, and phos, light." He lately read a paper in Reading, and exhibited his instrument. This consists of a receiving mirror, the wires, a battery, and a reproducing speculum. The receiving mirror is an amalgam of selenium and iodide of silver; the reproducing speculum is a compound of selenium and chromium. The wires are numerous, as it is necessary for distinctness that a wire should be required to affect but a very small space. The instrument exhibited had a mirror six inches by four, composed of seventy-two small plates to each of which a wire was attached, the whole being wrapped by a fine insulated covering. These wires run to a common galvanic battery and thus connect with the reproducing plate. When the circuit is closed, the rays of light are conducted through an ordinary camera, and the accompanying heat produces chemical changes in the the amalgam of the mirror, which, modifying the electric current, cause similar changes in the reproducing speculum. In the experiments at the close of the explanatory lecture, an instrument was taken to a lower room of the building and operated from there to the stage in the presence of the audience. Before the mirror in the lower room the committee held in succession an apple, a pen knife, and a trade dollar, which were distinct on the platform above. The date on the trade dollar, thrown on an enlarged screen, was plainly visible, as well as the goddess of liberty. A watch was next used, and the audience could see the movement of the hands. An ink bottle, a flower, parts of a theatre hand-bill, were also shown, and when the head of a live kitten was exhibited, there was great applause, and the inventor warmly congratulated on his success. The opinions entertained of its practical value are very high-it being possible for a signal officer on a railroad to see hundreds of miles of track at the same instant."

We are informed by a gentlemen residing near New York, that during a visit to France a few years ago, his attention was called to the successful attempt of the police authorities aided by a Scientest, to reproduce at a distant city by telegraph the features of a criminal who was fleeing from justice. In this case the means employed were perfectly successful, and the results obtained identical to those claimed in the "Diaphote."

There are other methods by which "seeing by tele

graph" can be accomplished. Professor Graham Bell has deposited with the Smithsonian Institute a sealed description of an instrument he has invented, which has caused Messrs. Ayrton & Perry of England, who have been working on the same problem, to offer the following statement, which indicates the means they employ:

"While we are still quite in ignorance of the nature of this invention, it may be well to intimate that com plete means for seeing by telegraphy have been known for some time by scientific men. The following plan has often been discussed by us with our friends, and no doubt has suggested itself to others acquainted with the physicial discoveries of the last four years. It has not been carried out because of its elaborate nature and on account of its expensive character. Nor should we recommend its being carried out.

Our transmitter at A—that is, the apparatus for receiving the light impressions and transmitting them electrically-consisted of a large surface made up of very small separate squares of selenium. One end of each piece was connected by an insulated wire to the distant place, and the other end of each piece with the ground, in accordance with the plan commonly employed with telegraph instruments. The object whose image was to be sent by telegraph was illuminated very strongly, and by means of a lens a very large image was thrown on the surface of the above transmitter. Now, it is well known if each little piece of selenium forms part of a circuit in which there is a constant electromotive force, say of a voltaic battery, the current passing through each piece will depend on its illumination. Hence, the strength of the electric illumination of its extremity. Our receiver at the current in each telegraph line will depend on the other end, B, was, in our original plan, a collection of magnetic needles, the movements of each of which (as in the ordinary needle telegraph) were controlled by the electric current passing through the particular telegraph wire with which it was in connection. Each magnet by its movement closed or opened an aperture through which light passed to illuminate the back of a sheet of frosted glass. There were, of course, as many of the illuminated squares at B as of selenium squares at A, and it is quite evident that since the illumination of each receiving square depends on the strength of the current in its circuit, and this current again depends on the illumination of the selenium at the other end of the wire, the image of a distant object might in this way be transmitted as a mosaic by electricity.

A more promising arrangement, suggested by Professor Kerr's experiments, consisted in having each square at B made of silvered soft iron, and forming the end of the core of a little electro-magnet, round which passed the current, coming from the corresponding selenium square at the other end. We proposed that the surface formed by these squares at B should be illuminated by a great beam of light, polarized by reflection from glass, and received again by an analyzer. It is then evident that since the intensity of the analyzed light depends on the rotation of the plane of polarization, by each little square of iron, and this depends on the strength of the current, and that again on the illumination of the selenium, we have another

method of receiving at B the illumination of the little squares at A."

Even this plan appears to have been anticipated in one sense two years ago, by Mr. J. E. H. Gordon of London, who says:

"I used an electromagnet consisting of an iron bar 2 feet 4 inches long and 2 inches in diameter, surrounded by 70 lbs. of wire, and excited by ten Grove cells.

The total double rotation produced, not by slightly altering the resistance, but by reversing the current, was never more than 26' (twenty-six minutes of arc).

To see this at all with a very delicate Jellett analyzer, it was necessary for the observer to increase the sensitiveness of his eye by sitting in total darkness for some ten minutes before each observation.

Your readers can judge what chance of obtaining visible changes of illumination there would be with 'little' magnets and mere variations in a current not powerful enough to fuse a selenium resistance."

Lastly we may offer an apparatus arranged by Mr. Middleton of Cambridge, England, who gives the following account of it :

"A lens is used to throw on a plane or suitably curved receiving plate (inclosed in a camera) the image of any object. The receiving plate of the camera is composed of thermopile elements, ground to a smooth surface, and having their posterior faces put in electrical communication by a system of wires, with a somewhat similarly constructed plate. The heating, &c., effect of the image on the first plate generates currents of electricity, which flow through the wire system, and on reaching the second thermopile plate are reconverted into heat, &c., according to the law discovered by Peltier, the amount of heat, &c., being directly proportional to the amount of electricity.

Moreover, according to the manner in which the elements of the plate are arranged with respect to each other, we can get a 'positive' or 'negative' (to use the ordinary phraseology of photography) picture on the second receiving plate, since the Peltier effect here holds, and the copy of a picture depends solely on establishing a constant ratio in the radiant heat and light which corresponding points of the picture and copy send to the eye.

Furthermore, these images can be either viewed directly or by reflected light (after the fashion of the the Japanese mirrors and projection on a screen), or by suitable apparatus they can be retained as a photograph, a thermograph, or chemicograph, the details of which will be found in the paper alluded to, and of which an abstract will, I believe, soon appear in the Proceedings of the Cambridge Philosophical Society. Also, I touched upon the method of attacking the problem of photographing in colors, and in conclusion pointed out a striking anology between the camera of the instrument and that of the human eye; the thermo-electric elements of the instrument and the rods and the cones of the eye; the conducting system of insulated wires emanating from the plate of the instrument and the optic nerve (or bundle of conducting fibres of the eye)—supposing that as the electric currents in the instruments effected a registration on the

sensitive paper, so in the eye the nerve currents of the optic nerve probably leave some brain trace on the mind."

It will thus be seen that while "seeing by telegraph" is not by any means a new invention, the principle involved is one full of interest, and as yet but partially developed; in this field of research ample scope will be found for those working in this direction and valuable results may be anticipated.

THE COMING OF AGE OF THE ORIGIN OF ́ SPECIES.'

Many of you will be familiar with the aspect of this small green-covered book. It is a copy of the first edition of the Origin of Species," and bears the date of its productionthe first of October, 1859. Only a few months, therefore, are needed to complete the full tale of twenty-one years since its birthday.

Those whose memories carry them back to this time will remember that the infant was remarkably lively, and that a great number of excellent persons mistook its manifestations of a vigorous individuality for mere naughtiness; in fact there was a very pretty turmoil about its cradle. My recollections of the period are particularly vivid; for having conceived a tender affection for a child of what appeared to me to be such remarkable promise, I acted for some time in the capacity of a sort of under-nurse, and thus came in for my share of the storms which threatened even the very life of the young creature. For some years it was undoubtedly warm work, but considering how exceedingly unpleasant the apparition of the new-comer must have been to those who did not fall in love with him at first sight, I think it is to the credit of our age that the war was not ficrcer, and that the more bitter and unscrupulous forms of opposition died away as soon as they did.

I speak of this period as of something past and gone, possessing merely a historical, I had almost said an antiquarian, interest. For, during the second decade of the existence of the "Origin of Species," opposition, though by no means dead, assumed a different aspect. On the part of all those who had any reason to respect themselves, it assumed a thoroughly respectful character. By this time the dullest began to perceive that the child was not likely to perish of any congenital weakness or infantile disorder, but was growing into a stalwart personage, upon whom mere goody scoldings and threatenings with the birch-rod were quite thrown away.

In fact, those who have watched the progress of science within the last ten years will bear me out to the full when I assert that there is no field of biological inquiry in which the influences of the "Origin of Species" is not traceable; the foremost men of science in every country are either avowed champions of its leading doctrines, or at any rate abstain from opposing them; a host of young and ardent investigators seek for and find inspiration and guidance in Mr. Darwin's great work; and the general doctrine of Evolution, to one side of which it gives expression, finds in the phenomena of biology a firm base of operations whence it may conduct its conquest of the whole realm of nature.

History warns us, however, that it is the customary fate of new truths to begin as heresies and to end as superstitions; and, as matters now stand, it is hardly rash to anticipate that, in another twenty years, the new generation, educated under the influences of the present day, will be in danger of accepting the main doctrines of the Origin of Species with as little reflection, and it may be with as little justification, as so many of our contemporaries, twenty years ago, rejected them."

Against any such a consummation let us all devoutly pray; for the scientific spirit is of more value than its products, and irrationally-held truths may be more harmful than reasoned errors. Now the essence of the scientific spirit is criticism. It tells us that to whatever doctrine claiming our assent, we should reply, take it if you can compel it. The struggle for existence holds as much in the

I A Lecture delivered at the Royal Institute, Friday, March 19.

intellectual as in the physical world. A theory is a species of thinking, and its right to exist is coextensive with its power of resisting extinction by its rivals.

From this point of view it appears to me that it would be but a poor way of celebrating the Coming of Age of the Origin of Species were I merely to dwell upon the facts, undoubted and remarkable as they are, of its far-reaching influence and of the great following of ardent disciples who are occupied in spreading and developing its doctrines. Mere insanities and inanities have before now swollen to portentous size in the course of twenty years. Let us rather ask this prodigious change in opinion to justify itself; let us inquire whether anything has happened since 1859 which will explain, on rational grounds, why so many are worshipping that which they burned, and burning that which they worshipped. It is only in this way that we shall acquire the 'means of judging whether the movement we have witnessed is a mere eddy of fashion, or truly one with the irreversible current of intellectual progress, and, like it, safe from retrogressive reaction.

Every belief is the product of two factors: the first is the state of the mind to which the evidence in favor of that belief is presented; and the second is the logical cogency of the evidence itself. In both these respects the history of biological science during the last twenty years appears to me to afford an ample explanation of the change which has taken place; and a brief consideration of the salient events of that history will enable us to understand why, if the Origin of Species" appeared now, it would meet with a very different reception from that which greeted it in 1859. One-and-twenty years ago, in spite of the work commenced by Hutton, and continued with rare skill and patience by Lyell, the dominant view of the past history of the earth was catastrophic. Great and sudden physical revolutions, wholesale creations and extinctions of living beings, were the ordinary machinery of the geological epoch brought in fashion by the misapplied genius of Cuvier. It was gravely maintained and taught that the end of every geological epoch was signalized by a cataclysm, by which every living being on the globe was swept away, to be replaced by a brand-new creation when the world returned to quiescence. A scheme of nature which appeared to be modelled on the likeness of a succession of rubbers of whist, at the end of each of which the players upset the table and called for a new pack, did not seem to shock anybody.

I may be wrong, but I doubt if at the present time there is a single responsible representative of these opinions left. The progress of scientific geology has elevated the fundamental principle of uniformitarianism, that the explanation of the past is to be sought in the study of the present, into the position of an axiom; and the wild speculations of the catastrophists, to which we all listened with respect a quarter of a century ago, would hardly find a single patient hearer at the present day. No physical geologist now dreams of seeking outside the ranges of known natural causes for the explanation of anything that happened millions of years ago, any more than he would be guilty of the like absurdity in regard to current events.

The effect of this change of opinion upon biological speculation is obvious. For, if there have been no periodical general physical catastrophes, what brought about the assumed general extinctions and re-creations of life which are the corresponding biological catastrophes? And if no such interruptions of the ordinary course of nature have taken place in the organic, any more than in the inorganic world, what alternative is there to the admission of Evolution?

The doctrine of Evolution in Biology is the necessary result of the logical application of the principles of uniformitarianism to the phenomena of life. Darwin is the natural successor of Hutton and Lyell, and the "Origin of Species" the natural sequence of the " Principles of Geology."

The fundamental doctrine of the "Origin of Species," as of all forms of the theory of Evolution applied to biology, is "that the innumerable species, genera, and families of organic beings with which the world is peopled have all descended, each within its own class or group, from common parents, and have all been modified in the course of descent." i

I Origin of Species," ed. 1, p. 457.

And, in view of the facts of geology, it follows that all living animals and plants" are the lineal descendants of those which lived long before the Silurian epoch."1

It is an obvious consequence of this theory of Descent with Modification, as it is sometimes called, that all plants and animals, however different they may now be, must, at one time or other, have been connected by direct or indirect intermediate gradations, and that the appearance of isolation presented by various groups of organic beings must be unreal.

No part of Mr. Darwin's work ran more directly counter to the prepossessions of naturalists twenty years ago than this. And such prepossessions were very excusable,for there was undoubtedly a great deal to be said, at that time, in favor of the fixity of species and of the existence of great breaks, which there was no obvious or probable means of filling up, between various groups of organic beings.

For various reasons, scientific and unscientific, much had been made of the hiatus between man and the rest of the higher mammalia, and it is no wonder that issue was first joined on this part of the controversy. I have no wish to revive past and happily forgotten controversies, but I must state the simple fact that the distinctions in cerebral and other characters, which were so hotly affirmed to separate man from all other animals in 1860, have all been demonstrated to be non-existent, and that the contrary doctrine is now universally accepted and taught.

But there were other cases in which the wide structual gaps asserted to exist between one group of animals and another were by no means fictitious; and, when such structual breaks were real, Mr. Darwin could account for them only by supposing that the intermediate forms which once existed had become extinct. In a remarkable passage he

says:

"We may thus account even for the distinctness of whole classes from each other-for instance of birds from all other vertebrate animals-by the belief that many animal forms of life have been utterly lost, through which the early progenitors of birds were formerly connected with the early progenitors of the other vetebrate classes." *

Adverse criticism made merry over such suggestions as these. Of course it was easy to get out of the difficulty by supposing extinction; but where was the slightest evidence that such intermediate forms between birds and reptiles as the hypothesis required ever existed? And then probably followed a tirade upon this terrible forsaking of the paths of "Baconian induction."

But the progress of knowledge has justified Mr. Darwin to an extent which could hardly have been anticipated. In 1862, the specimen of Archeopteryx, which until the last two or three years has remained unique, was discovered; and it is an animal which, in its feathers and the greater part of its organization, is a veritable bird, while, in other parts, it is as distinctly reptilian.

In 1868, I had the honour of bringing under your notice, in this theatre, the results of investigations made, up to that time, into the anatomical characters of certain ancient reptiles, which showed the nature of the modifications in virtue of which the type of the quadrupedal reptile passed into that of the bipedal bird; and abundant confirmatory evidence of the justice of the conclusions which I then laid before you has since come to light.

In 1875, the discovery of the toothed birds of the cretaceous formation in North America, by Prof. Marsh, completed the series of transitional forms between birds and reptiles, and removed Mr. Darwin's proposition that many animal forms of life have been utterly lost, through which the early progenitors of birds were formerly connected with the early progenitors of the other vertebrate classes," from the region of hypothesis to that of demon

strable fact.