Address of Sir Joseph Dalton Hooker, C.B., K.C.S.I. The President,

Delivered at The Anniversary Meeting of The Royal Society, on Saturday, November 30, 1878.

Editor’s note: the printed pamphlet’s original page numbers are shown in brackets [5] to make it easier to cite this version, and the page breaks are shown with a thin red line. The original title page and its blank reverse had no numbers and the first page of text was numbered 3. The original footnotes are shown in the positions where they originally occurred.

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Hooke demonstrated its cellular structure, and by an interesting coincidence he was one of the first to investigate, at the request, indeed, of the founder of the Society, Charles II, the movements of the sensitive plant Mimosa pudica—one of a class of phenomena which is still occupying the attention of more than one of our Fellows. In attributing the loss of turgescence, which is the cause of the collapse of the petiole and subordinate portions of the compound leaf which it supports, to the escape of a subtle humour, he to some extent foreshadowed the modern view which attributes the collapse of the cells to the escape of water by some mechanism far from clearly understood—whether from the cell-cavities, or from the cell-walls into the intercellular spaces.

Hooke having shown the way, Nehemiah Grew, who was also Secretary of the Royal Society, and Marcello Malpighi, Professor of Medicine in the University of Bologna, were not slow to follow it. Almost simultaneously (1671–3) the researches of these two indefatigable students were presented to the Royal Society, and the publication of two editions of Malpighi’s works in London proves how entirely this country was at that time regarded as the head quarters of this branch of scientific inquiry. We owe to them the generalisation of the cellular structure, which Hooke had ascertained in cork, for all other vegetable tissues. They described also accurately a host of microscopic structures then made known for the first time. Thus, to give one example, Grew figured and described in several different plants the stomata of the epidermis: —”Passports,” as he writes, “either for the better avolation of superfluous sap, or the admission of air.”

With the exception of Leeuwenhoek no observer attempted to make any substantial addition to the labours of Grew and Malpighi for more than a century and a half, and however remarkable is the impulse which he gave to morphological studies, the view of Caspar Wolff in the middle of the 18th century (1759), in regarding cells as the result of the action of an organizing power upon a matrix, and not as themselves influencing organization, were adverse to the progress of histology. It is from Schleiden (1838) who described the cell as the true unit of vegetable structure, and Schwann who extended this view to all organisms whether plants or animals, and gave its modern basis to biology by reasserting the unity of organization throughout animated nature, that we must date the modern achievements of histological science. Seldom, perhaps, in the history of science has any one man been allowed to see so magnificent a development of his ideas crate the space of his own lifetime as has slowly grown up before the eyes of the venerable Schwann, and it was, therefore, with peculiar pleasure that a letter of congratulation was entrusted by your Officers to one of our Fellows on behalf of this Society on the recent occasion of the celebration of the 40th anniversary of Schwann’s entry into the professorate.

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If we call up in our mind’s eye some vegetable organism and briefly reflect on its construction, we see that we may fix on three great steps in the analysis of its structure, the organic, the microscopic, and the molecular, and, although not in the same order, each of the three last centuries is identified with one of these. In the 17th century Grew achieved the microscopic analysis of plant tissues into their constituent cells; in the 18th, Caspar Wolff effected the organic analysis (independently but long subsequently expounded by the poet Goethe) of plant structures into stem and leaf. It remained for Nägeli in the present century to first lift the veil from the mysterious processes of plant growth, and by his memorable theory of the molecular constitution of the starch-grain and cell-wall, and their growth by intussusception (1858), to bring a large class of vital phenomena within the limits of physical interpretation. Strasburger has lately (1876) followed Sachs in extending Nägeli’s views to the constitution of protoplasm itself, and there is now reason to believe that the ultimate structure of plants consists universally of solid molecules (not however identical with chemical molecules) surrounded with areas of water which may be extended or diminished. While the molecules of all the inert parts of plants (starch-grains, cell-wall, &c.) are on optical grounds believed by most physiologists to have a definite crystalline character, no such conclusion can be arrived at with respect to the molecules of protoplasm. In these molecules the characteristic properties of the protoplasm reside, and are more marked in the aggregate mass in proportion to its denseness, and this is due to the close approximation of the molecules and the tenuity of their watery envelopes. The more voluminous the envelopes, the more the properties of protoplasm merge in those of all other fluids.

It is, however, to the study of the nuclei of cells that attention has been recently paid with the most interesting results. These well-known structures, first observed by Ferdinand Bauer at the beginning of the century (1802), were only accurately described thirty years later by Robert Brown (1833). Up to the present time their function has been extremely obscure. The beautiful investigations of Strasburger (1875) have led him to the conclusion that the nucleus is the seat of a central force which has a kind of polarising influence upon the protoplasm molecules, causing them to arrange themselves in lines radiating outwards. Cell-division he regards as primarily caused by the nucleus becoming bipolar, and the so-called caryolitic figures first described by Auerbach, exhibit the same arrangement of the protoplasm molecules in connecting curves as in the case of iron-filings about the two poles of a bar-magnet. The two new centres mutually retire, and each influencing its own tract of protoplasm, the cell-division is thereby ultimately effected. This is but a brief account of processes which are greatly complicated in

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actual detail, and of which it must be remarked that while the interest and beauty of the researches are beyond question, caution must be exercised in accepting the mechanical speculations by which Strasburger attempts to explain them. He has himself shown that cell-division presents the same phenomena in the animal kingdom; a result which has been confirmed by numerous observers, amongst whom I may content myself with mentioning one of our own Society, Mr. F. Balfour. Strasburger further points out that this affords an argument for the community of descent in animal and vegetable cells; he regards free cell-division as derivable from ordinary cell-division by the suppression of certain stages.

Turning now to the discoveries made during the last five years in Physiological Botany, we find that no one has advanced this subject so greatly as Mr. Darwin. In 1875 was published his work on Insectivorous Plants, in which he ascertained the fact that a number of species having elaborate structures adapted for the capture of insects, utilized the nitrogenous matter which these contain as food. The most important principle established in the course of these researches was, that such plants as Drosera, Dionoea, Pinguicula, secrete a digestive fluid, which has led through Gorup Bezanez’s investigations on the ferment in germinating seeds, to a recognition of the active agency of ferments in the transmission of food-material, which marks a great advance in our knowledge of the general Physiology of Nutrition.

The extreme sensitiveness of the glands of Drosera to mechanical and chemical stimulus (especially to phosphate of ammonia), the directive power of its tentacles, depending upon the accurate transmission of motor impulses, and the “reflex” excitation of secretion in the glands, were all discoveries of the most suggestive nature in connexion with the subject of the irritability and movements of plants. The phenomenon of the aggregation of the protoplasmic cell-contents in the tentacles of Drosera is a discovery of a highly remarkable nature, though not yet thoroughly understood. Lastly, Mr. Frank Darwin, following his father’s footsteps, as it were crowned the edifice by showing to what an extent insectivorous plants do profit by nitrogenous matter supplied to their leaves.

In close relation to these researches are those, also by Mr. Darwin, on the structure and functions of the bladder of Utricularia, which he has shown to have the power of absorbing decaying animal matter; and those of Mr. Frank Darwin on contractile filaments of extraordinary tenuity attached to the glands on the inner surface of the cups formed by the connate bases of the leaves of the Teasel, which filaments exhibit motions suggesting a protoplasmic origin. It is to be hoped that their discoverer will pursue his investigations into these curious bodies, whose origin and real nature in relation to the plant and its functions are involved in obscurity.

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The subject of the cross-fertilization of plants, which though a long known phenomenon, first become a fruitful scientific study in Mr. Darwin’s now classical work “On the various contrivances by which Orchids are fertilized,” has within the last few years made rapid advance under its author’s hand. The extreme importance of avoiding self-fertilization might indeed be inferred from the prevalence in flowers of elaborate contrivances for preventing it; but it remained to be shown that direct benefit attended cross-fertilization, and this has now been proved by an elaborate series of experiments, the results of which are not only that both increased fertility or greater vigour of constitution attend cross-fertilization, but that the opposite effects attend self-fertilization. In the course of these experiments it became evident that the good effects of the cross do not depend on the mere fact of the parents being different individuals, for when these were grown together and under the same conditions, no advantage was gained by the progeny; but when grown under different conditions a manifest advantage was gained. As instances, if plants of Ipomoea and Mimulus, which had been self-fertilized for seven previous generations, were kept together and then intercrossed, their offspring did not profit in the least; whereas, when the parent plants were grown under different conditions, a remarkably vigorous offspring was obtained.

Mr. Darwin’s last work, “On the different forms of Flowers,” though professedly a reprint of his paper on dimorphic plants, published by the Linnaean Society, contains many additions and new matter of great importance concerning the behaviour of polygamous plants, and on Cleistogamic flowers. Among other points of great interest is the establishment of very close analogies between the phenomena attending the illegitimate union of trimorphic plants, and the results of crosses between distinct species, the sterile offspring of the crosses of the same species exhibiting the closest resemblance to the sterile hybrids obtained by crossing distinct species; while a whole series of generalizations, founded on the results of the one series of experiments, are closely paralleled by those founded on the other. The bearing of this analogy on the origin of species is obviously important.

Besides these investigations, Mr. Darwin has produced within the last five years second editions of his volume on the Fertilization of Orchids, and on the Habits and Movements of Climbing Plants; as also of his early works on Coral Reefs, and Geological Observations in South America; all of them abounding in new matter.

Of special interest to myself, as having been conducted in the Jodrell Laboratory at Kew, are Dr. Burdon Sanderson’s investigations on the exceptional property possessed by the leaves and other organs of some plants which exhibit definite movements in

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response to mechanical, chemical, or electric stimuli. In 1873, Dr. Sanderson showed us in this meeting room, that the closing of the laminae of the leaf of Dionoea is preceded by a preliminary state of excitement, and is attended with a change in the electric conditions of the leaf; and this so closely resembled the change which attends the excitation of the excitable tissues of animals, that he did not hesitate to identify the two phenomena.

This remarkable discovery immediately directed the attention of two German observers to the electromotive properties of plants, one, Dr. Kunkel, in the Laboratory of Professor Sachs; the other Professor Munk, in that of the University of Berlin.

Professor Munk, whose researches are of much the greater scope and importance, took as his point of departure Dr. Burdon Sanderson’s discovery. The leading conclusion to which he arrived was, that in Dionoea each of the oblong cells of the parenchyma is endowed with electromotive properties, which correspond with those of the “muscle-cylinder” of animals; with this exception, that whereas in the muscle-cylinder the ends are negative to the central zone, in the vegetable cell they are positive; and he endeavours to prove, that according to this theory, all the complicated electromotive phenomena which had been observed, could be shown to be attributable to the peculiar arrangement of the leaf-cells.

During the last two summers Dr. Burdon Sanderson has been engaged in endeavouring to discover the true relations which subsist between the electrical disturbance, followed by the shutting of the leaf-valves of Dionoea and the latent change of protoplasm which precedes this operation. He has found that though the mechanism of the change of form of the excitable parenchyma which causes the contraction is entirely different from that of muscular contraction, yet that the correspondence between the exciting process in the animal tissues, and what represents this in plant tissues appears to be more complete the more carefully the comparison is made; and that whether the stimulus be mechanical, thermal, or electrical, its effects correspond in each case. Again, the excitation is propagated from the point of excitation to distant points in the order of their remoteness, and the degree to which the structure is excited depends upon its temperature. Notwithstanding, however, the striking analogies between the electrical properties of the cells of Dionoea and of muscle-cylinders, Dr. Burdon Sanderson is wholly unable to admit with Professor Munk that these structures are in this respect comparable.

In Morphological Botany attention has been especially directed of late to the complete life-history of the lower order of Cryptogams, since this is seen to be more and more an indispensable preliminary to any attempt at their correct classification.

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The remarkable theory of Schwendener, now ten years old, astonished botanists by boldly sweeping away the claims to autonomous recognition of a whole group of highly characteristic organisms—the Lichens—and by affirming that these consist of asco-mycetal fungi united in a commensal existence with Algae. The controversial literature and renewed investigations which this theory has given rise to are now very considerable. But the advocates of the Schwendenerian view have gradually won their ground, and the success which has attended the experiments of Stahl in taking up the challenge of Schwendener’s opponents and manufacturing such lichens as Endocarpon and Thelidium, by the juxtaposition of the appropriate Algae and Fungi, may almost be regarded as deciding the question. Sachs, in the last edition of his Lehrbuch, has carried out completely the principle of classification of Algae, first suggested by Cohn, and has proposed one for the remaining Thallophytes, which disregards their division into Fungi and Algae. He looks upon the former as standing in the same relation to the latter as the so-called Saprophytes (e. g. Neottia) do to ordinary green flowering-plants.

This view has especial interest with regard to the minute organisms known as Bacteria, a knowledge of the life-history of which is of the greatest importance, having regard to the changes which they effect in all lifeless and, probably, in all living matter prone to decomposition. This affords a morphological argument (as far as it goes) against the doctrine of Spontaneous Generation, since it seems extremely probable that just as yeast may be a degraded form of some higher fungus, Bacteria, may be degraded allies of the Oscillatoriae which have adopted a purely saprophytal mode of existence.

Your “Proceedings” for the present year contain several important contributions to our knowledge of the lowest forms of life. The Rev. W. H. Dallinger, continuing those researches which his skill in using the highest microscopic powers and his ingenuity in devising experimental methods have rendered so fruitful, has adduced evidence which seems to leave no doubt that the spores or germs of the monad which he has described differ in a remarkable manner from the young or adult monads in their power of resisting heated fluids. The young and adult monads, in fact, were always killed by five minutes’ exposure to a temperature of 142· F. (61· C. ), while the spores germinated after being subjected to a temperature of ten degrees above the boiling point of water (222· F. ).

Two years ago, Cohn and Koch observed the development of spores within the rods of Bacillus subtilis and B. anthracis. These observations have been confirmed, with important additions, in these two species by Mr. Ewart, and have been extended to the Bacillus of the infectious pneumo-enteritis of the pig, by Dr. Klein; and to Spirillum by Messrs. Geddes and Ewart; and thus a very important step has

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been made towards the completion of our knowledge of the life-history of these minute but important organisms. Dr. Klein has shown that the infectious pneumo-enteritis, or typhoid fever of the pig, is, like splenic fever, due to a Bacillus, Having succeeded in cultivating this Bacillus in such a manner as to raise crops free from all other organisms, Dr. Klein inoculated healthy pigs with the fluid containing the Bacilli, and found that the disease in due time arose and followed its ordinary course. It is now therefore, distinctly proved that two diseases of the higher animals, namely, “splenic fever” and “infectious pneumo-enteritis,” are generated by a contagium vivum.

Finally, Messrs. Downes and Blunt have commenced an enquiry into the influence of light upon Bacteria and other Fungi, which promises to yield results of great interest, the general tendency of these investigations leaning towards the conclusion that exposure to strong solar light checks and even arrests the development of such organisms.

The practical utility of investigations relating to Bacillus organisms as affording to the pathologist a valuable means of associating by community of origin various diseases of apparently different character, is exemplified in the “Loodiana fever,” which has been so fatal to horses in the East. The dried blood of horses that had died of this disease in India has been recently sent to the Brown Institution, and from seeds therein contained a crop of Bacillus anthracis has been grown, which justified its distant pathological origin by reproducing the disease in other animals. Other equally interesting experiments have been made at the same Institution, showing that the “grains” which are so largely used as food for cattle, afford a soil which is peculiarly favourable for the development and growth of the spore filaments of Bacillus; and that by such “grains” when inspected, the anthrax fever can be produced at will, under conditions so simple that they must often arise accidentally. The bearing of this fact on a recent instance in which anthrax suddenly broke out in a previously uninfected district, destroying a large number of animals, all of which had been fed with grains obtained from a particular brewery, need scarcely be indicated.

In Systematic Botany, which in a nation like ours, ever extending its dominions and exploring unknown regions of the globe, must always absorb a large share of the energies of its phytologists, I can but allude to two works of great magnitude and importance.

Of these, the first is the “Flora Australiensis” of Bentham, completed only a year ago; a work which has well been called unique in botanical literature, whether for the vast area whose vegetation it embraces (the largest hitherto successfully dealt with), or for the masterly manner in which the details of the structure and affinities of upwards of 8, 000 species have been elaborated. Its value in reference

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to all future researches regarding the geographical distribution of plants in the southern hemisphere, and the evolution therein of generic and specific types, cannot be over estimated.

The other great work is the “Flora Braziliensis,” commenced by our late Foreign Fellow, von Martius, and now ably carried on by Eichler, of Berlin, assisted by coadjutors (among whom are most of our leading systematists) under the liberal auspices of His Majesty the Emperor of Brazil. When completed, this gigantic undertaking will have embraced, in a systematic form, the vegetation of the richest botanical region of the globe.

Having now endeavoured to recall to you some of the great advances in Science made during the last few years, it remains for me, after the distribution of the Medals awarded by your Council, to retire from the Presidency in which I have so long experienced the generous support of your Officers and yourselves. This support, for which I tender you my hearty thanks, together with my sense of the trust and dignity of the office, and the interest attached to its duties, make my resignation of it a more difficult step than I had anticipated. My reasons are, however, strong. They are the pressure of official duties at Kew, annually increasing in amount and responsibility, together with the engagements I am under to complete scientific works, undertaken jointly with other botanists, before you raised me to the Presidency; and the fact that indefinite postponement delays the publication of the labours of my coadjutors. I am also influenced by the consideration that, though wholly opposed to the view that the term, of the Presidency of the Royal Society should be either short or definitely limited, this term should not be very long; and that, considering the special nature of my own scientific studies, it should, in my case, on this as well as on other grounds, be briefer than might otherwise be desirable. Cogent as these reasons are, they might not have been paramount, were it not that we have among us, one pre-eminently fitted to be your President by scientific attainments, by personal qualifications, and by intimate knowledge of the Society’s affairs; and by calling upon whom to fill the proud position which I have occupied, you are also recognising the great services he has rendered to the Society as its Treasurer for eight years, and its ofttimes munificent benefactor.

The Copley Medal has been awarded to Jean Baptiste Boussingault for his long-continued and important researches and discoveries in agricultural chemistry.

The researches of Boussingault have extended over nearly half a century, and it might be difficult to find an investigator whose results relating to a great variety of subjects have in respect of accuracy and trustworthiness better stood the test of time.

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The lucid simplicity with which his writings narrate well-established and well-arranged facts, is not less remarkable than the judicial caution with which he has abstained from expressing opinions upon questions beyond the reach of decisive evidence.

His experimental results and the conclusions which he has drawn from them have been deservedly trusted by other workers in the same field, and have safely guided them in their labours. Their incontestable excellence has prevented them from becoming subjects of animated discussion, and thus arousing as much attention and interest in the outer world as has sometimes been aroused by hasty experiments and daring generalizations.

I cannot attempt within the limits of this address to give an account of his investigations, and I should probably weary you were I even to enumerate them, relating as they do to a vast variety of phenomena; but I may point out that lying as most of them do in the domain of agricultural chemistry, they have involved difficulties of no common order. Boussingault is not only an excellent chemical analyst and experimentalist, but at the same time a model farmer.

His numerous determinations of the nitrogen, carbon, and hydrogen in crops and in the manures supplied to them, have proved him to be skilled not only in selecting and applying the best known methods of analysis, but even in improving and perfecting them.

His determinations of the proportions of those valuable constituents of manures which can be assimilated by various crops, have involved an intimate acquaintance with the conditions which experience has proved to be most favourable to the cultivation of the various crops.

His numerous and varied experiments on the feeding of animals, showing the proportions between the nitrogenized and fatty or amylaceous constituents supplied in the food and those assimilated or formed by the animal organism, while tracing the distribution of the remainder between the pulmonary and other excretions, have had most important physiological as well as practical bearings.

In all his investigations we see proofs that while accurately and critically acquainted with the discoveries and opinions of other workers and thinkers in his own particular domain of science, he has been able to devise and carry out simple and crucial forms of experiment well calculated to decide the truth.

A remarkable instance of this is afforded by those truly masterly experiments by which he proved that all the nitrogen found in the organism of plants can be traced to compounds of that element which had been supplied to them; and accordingly that there are no grounds for believing that plants can assimilate the free nitrogen of the air.

By awarding to Boussingault the Copley Medal, we place his name in the honoured list of those who, in modern times, have rendered the highest services to the advancement of natural knowledge.

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A Royal Medal has been awarded to Mr. John Allan Broun for his investigations during thirty-five years in magnetism and meteorology, and for his improved methods of observation.

When the labours of Gauss had given an impetus to the study of terrestrial magnetism by rendering precision possible, Observatories devoted to this branch of research, in conjunction with meteorology, began to rise in various places. The late General Sir T. M. Brisbane erected one at Makerstown, in Scotland, and placed it under the direction of Mr. Broun, who remained in charge of it from 1842 to 1850. His observations and their results, have been commended by magneticians and meteorologists, for the skill employed in the development of new methods of reduction and investigation.

In 1851 Mr. Broun went to India to organize and take charge of a similar Observatory established at Trevandrum by His Highness the late Rajah of Travancore. Here he remained for thirteen years, accumulating results of very great value, the first instalment of which, consisting of a volume on the magnetic declination, was published some years ago. Magneticians look eagerly towards the completion of this publication when the means necessary for the purpose shall have been furnished to Mr. Broun.

While in India he established an Observatory on a mountain peak 6,000 feet above the sea, and fitted it up with a very complete assortment of scientific instruments. This was an undertaking of a very arduous nature, effected in a wild country, and presenting great difficulties in the erection of instruments and obtaining trained observers.

Shortly after the commencement of magnetic observatories, Mr. Broun indicated the insufficiencies of the methods then in use for determining coefficients and correcting observations, and he devised new methods for these ends, the principal of which have been generally adopted.

This is not the place in which to give a complete catalogue of Mr. Broun’s researches in magnetism and meteorology, extending as they do over a period of thirty-five years, but I may indicate those of his results that are of the greatest importance. Among them are the establishment of the annual laws of magnetic horizontal force, exhibiting maxima at the solstices and minima at the equinoxes. Mr. Broun was also the first to give in a complete form the laws of change of the solar-diurnal variation of magnetic declination near the equator, showing the extinction of the mean movement near the equinox. His researches on the lunar-diurnal variation of magnetic declination are of very great interest. Besides being an independent discoverer of the existence of this variation, he showed that near the equator its law in December was the opposite of that in June. He found, too, that the lunar-diurnal variation was in December sometimes greater than the solar-diurnal variation—that the lunar action

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was reversed at sunrise, and that it was much greater during the day than during the night, whether the moon was above or below the horizon. Finally, he found that the lunar-diurnal law changed (like the solar-diurnal law at the equator) near the equinoxes, so that, as a consequence, the laws for the southern and northern hemispheres were of opposite natures.

Another and very remarkable fact discovered by Mr. Broun was that the variations from day to day of the earth’s daily mean horizontal force were nearly the same all the world over. He found certain oscillations in these daily means which were due to the moon’s revolution, and others having a period of twenty-six days; the latter he considered as due to the sun’s rotation. It results from these investigations that the observed variations of the earth’s daily mean horizontal force have been represented with considerable accuracy in all their more marked features, by the combination of the means calculated for these different solar and lunar periods. During the discussion of these periods, Mr. Broun found that the great magnetic disturbances were apparently due to actions proceeding from particular points or meridians of the sun—a fact this (if verified) of very great importance.

In meteorology he has shown the apparent simultaneity of the changes of daily mean barometric pressure over a great part of the globe, and he has likewise discovered a barometric period of twenty-six days nearly. He was also the first to commence and carry out, during several years, a systematic series of observations of the motions of clouds at different heights in the atmosphere; and, lastly, he has found certain laws connecting the motions of the atmosphere, and the directions of the lines of equal barometric pressure.

A Royal Medal has been awarded to Dr. Albert Günther, F.R.S., for his numerous and valuable contributions to the zoology and anatomy of fishes and reptiles.

Dr. Günther’s labours as a systematist and a descriptive zoologist have been devoted chiefly to the order of Fishes, Reptiles, and Amphibia. Upon these he has published during the last quarter of a century a very long series of valuable papers, whereby our knowledge of the structure, affinities, and distribution of the genera and species of those interesting groups has been greatly advanced. We owe to his indefatigable exertions the excellent condition in point of arrangement and nomenclature of the unrivalled collection of fishes in the British Museum, and of which he prepared a systematic catalogue in eight volumes, which has been published by order of the Trustees. This is a work of prodigious labour; it required for its satisfactory execution an intimate knowledge of the fish of all parts of the world, and an intuitive perception of the natural character upon which a sound classification should be based. From possessing these attributes it has been

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accepted as the standard authority on the order by all zoologists. Under this head too I must specially allude to his excellent work on the Ceratodus. The Reptilian collections of the Museum have been no less successfully dealt with by Dr. Günther, and have afforded the material for some of his most important works, amongst which his “Reptiles of British India,” “Memoir on Hatteria,” and “Monograph of the Gigantic Land Tortoises of certain islands in the Pacific and Indian Oceans,” are examples conspicuous for their completeness and accuracy.

The Rumford Medal has been awarded to Mr. Alfred Cornu for his various Optical Researches, and especially for his recent redetermination of the Velocity of Propagation of Light.

Mr. Alfred Cornu is the author of papers on optical and other subjects published in the “Comptes Rendus” and other scientific periodicals. He has been engaged, for example, with the difficult subject of crystalline reflection, and kindred researches.

It was in 1849 that Fizeau astonished the scientific world by an actual experimental determination of the velocity of light, a velocity so enormous that hitherto its finiteness has been proved, and its value approximately determined, only by two astronomical phenomena. Foucault almost simultaneously brought out an experimental determination by a totally different method.

The method of Fizeau gave at once a near approximation to the value got from those two astronomical phenomena, combined with the parallax of the sun, assumed known. But the difficulties of obtaining a sufficiently accurate result were such that the velocity obtained by Fizeau’s method was not considered to rival in exactness the velocity determined astronomically. Indeed, Foucault’s method seemed to be preferred, though Fizeau’s is the simpler in principle, and is free from certain doubts which may be raised as regards the other. But the difficulties alluded to, which turned mainly on the determination of the velocity of the revolving wheel, were such that almost twenty years have elapsed without the method having been brought to a sufficient degree of perfection to make it astronomically available.

Such was the state of the problem when it was taken up by M. Cornu. By methods of his own devising he succeeded in getting over the difficulties with which Fizeau’s further progress had been stopped, and in achieving a determination so exact as to compete with the astronomical determinations, and thereby lead, we may say, to an experimental determination of the solar parallax fully rivalling that which is likely to result from the observations of the transit of Venus which have been carried out at so much cost and trouble.

A double award of the recently instituted Davy Medal has again been

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made, the recipients on the present occasion being M. Louis Paul Cailletet and M. Raoul Pictet, This award is made to these distinguished men for having, independently and contemporaneously, liquefied the whole of the gases hitherto called permanent.

The methods pursued by these experimenters, in accomplishing results which equal in interest and importance those obtained by Faraday in the same direction fifty-five years ago, were quite distinct, and were, in each case, the result of several years’ preparatory labour. M. Cailletet, by comparatively very simple arrangements, such as admit of ready employment in lecture-demonstrations, has succeeded in obtaining evidence of the liquefaction, and possibly solidification, of carbonic oxide, marsh-gas, oxygen, nitrogen, and hydrogen. His system of operating consists in submitting the gases to very powerful compression at comparatively moderate degrees of cold, and in then allowing them very suddenly to expand.

M. Pictet has applied the very perfect system, elaborated and put to industrial use by him, for obtaining low temperatures to the attainment, though on a larger scale, of results like some of those arrived at by M. Cailletet. By an arrangement of vacuum and force pumps he reduces liquefied sulphurous acid to a low temperature, and applies this as the means for cooling down liquid carbonic acid which, in turn, serves to reduce to a very low temperature a thick glass tube, in which the gas to be condensed is confined at a very high pressure. M. Pictet has not only produced liquid oxygen in somewhat considerable quantity, and succeeded in determining its density, he has also obtained evidence of the solidification of hydrogen, and the description given of its appearance in the solid form seems to leave no doubt regarding its metallic character.

The interest which attaches to the remarkable experiments of MM. Cailletet and Pictet is only equalled by the importance of the fact, now absolutely demonstrated by those experiments, that the property of molecular cohesion is common to all known bodies without exception.

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