During his long tenure of a Fellowship in Trinity College, Prof. Sedgwick witnessed great changes in the mathematical training, and contributed as much as any man to the present favourable condition of Science in Cambridge. To defend the University against hasty imputations, to maintain a high standard of moral philosophy, and a PALMIERI'S VESUVIUS The Eruption of Vesuvius in 1872. By Prof. Palmieri, Director of the Vesuvian Observatory. With Notes and an Introductory Sketch, &c.. By Robert Mallet, F.R.S. (London: Asher and Co., 1873.) dignified preference for logical induction to alluring hyTHAT, in these days of rapid intercourse, the re-appear pothesis was always in his thoughts. Hence the "Discourse on the Studies of the University of Cambridge," at first an eloquent sermon, grew by prefix and suffix to a volume which he himself likened to a wasp-large in front and large behind, with a very fashionable waist. Under such feelings he spoke out against the "Vestiges of Creation" with a fervour of argument and declamation which must have astonished the unacknowledged author of that once popular speculation. Nor was he silent when the views of Darwin came to fill the void places of biological theory, against which he not only used a pen of steel but made great use of his heavy hammer. The vigour vehemence we may call it—of his pen and tongue in a matter which touched his sense of justice, morals, or religion, might mislead one who did not thoroughly know his truth and gentleness of heart, to suppose that anger was mixed with his honest indignation ου γαρ μειλιχος εσκε . . εν δαϊ λυγρῃ But it was quite otherwise. In a letter addressed to the writer, in reply to some suggestion of the kind, he gave the assurance that he was resolved "no ill blood" should be caused by the discussion which had become inevitable. He never failed in courtesy to the honest disputant whose arguments he mercilessly "contunded." Taken altogether, Professor Sedgwick was a man of grand proportion, cast in a heroic mould. Pressed in early life through a strict course of study, he found himself stronger by that training than most of his fellow geologists, but never made them feel his superiority. Familiar with great principles, and tenacious of settled truths, he was ready to welcome and encourage every new idea which appeared to be based on facts truly observed, and not unprepared or unwilling to stand, even if alone, against what he deemed unfair objection or unsubstantial hypothesis. This is not the place to speak of his private worth, or to indulge in reminiscence of his playful and exuberant fancy, the source of unfailing delight to those who knew him in his happier hours. Unmarried, but surrounded by plenty of cheerful relatives, his last hours of illness were soothed by sedulous affection; his kindly disposition no suffering could conceal; his lively interest in passing events nothing could weaken. Ever "Against oppression, fraud, or wrong, His voice rose high, his hand waxed strong." With collected mind, on the verge of the grave, he would express, with undiminished interest, his latest conclusions on his own Cambrian system, purely as a matter of scientific discussion, free from all personal considerations. It will be well if this mode of treatment be reverently followed by those who while speaking of Protozoic and Paleozoic Rocks, know enough to feel how much they have been benefited by the disinterested labours of a long and noble life. JOHN PHILLIPS ance of volcanic phenomena on the large scale in any part of the earth's surface should awaken a far more than mere local interest, was well illustrated in the case of the late great outbreak of Mount Vesuvius, during the continuance of which the telegraphic bulletins received from the fiery mountain became the subject of general inquiry and discussion in all parts of the civilised world; and even now that the eruption has entirely subsided, the publication of a translation by Mr. Mallet, of the report of the well-known Italian savant, Professor Palmieri, entitled "Incendio Vesuviano del 26 Aprile, 1872," will be welcomed as a valuable contribution to English scientific literature quite independently of its being a book likely to secure numerous readers amongst the non-scientific public also. This report of Professor Palmieri, who so courageously stuck to his post in the Observatory on the side of Mount Vesuvius, when that building actually stood between two torrents of liquid fire, the heat from which cracked the glass in the windows and even scorched the very habitation itself, is one of the most important records of volcanic phenomena which we possess. Written in the most unassuming style, it does not go into theoretical points, but confines itself all but entirely to recording such facts as were considered by its author to be important or interesting from a scientific point of view, alluding only incidentally to the destruction caused by the lava and ashes on the morning of April 26. In point of fact it is to be regarded as a scientific rather than a popular description of the eruption. Although the professor specially excels in details, the main features of the different phases of the eruption are well described, and a vivid impression of the enormous force developed on such occasions is conveyed by his observation that on April 26 the volume of smoke, ashes, lava fragments and bombs projected upwards from the crater attained a height of no less than 1,300 metres (4,265 feet) above its edge. The report itself contains a mass of data calculated to be of invaluable assistance in the future investigation of volcanic phenomena, and although it may be said that the conclusions arrived at from the study of this eruption, do not present us with any strikingly new or startling deduc. tions, their great value lies in the corroboration or correction of those resulting from previous observations. Amongst these may be mentioned, the opinion now held by the professor, that to a certain extent eruptions may be predicted, which he bases upon the observations that when the central crater commences to be agitated, this is followed by a series of slight convulsions which terminate in a grand outbreak or eruption, after which the volcano first settles down again into a state of repose; the evidence brought forward to prove the crystallisation of the leucite out of the fluid lava and against its pre-existence in it, as has been assumed by some previous writers; the order of appearance of the acid vapours; the constant presence of certain metallic compounds and sublimates; and the respective electrical conditions of the smoke and directly connected with the report on Vesuvius; and ashes. its style, which cannot be regarded as an agreeable one, is not very gracious to the labours of the many eminent men who have preceded or now hold views differing from those of the author. Although brought forward as representing the present state of knowledge of terrestrial vulcanicity, we find no reference to any of the continental men of science, who have done so much in this direction, and it should be more correctly entitled an exposition of the author's views on seismology and what he terms vulcanology, the first 46 pages being but an abstract of his previously published investigations into the phenomena of earthquakes. The report is illustrated by eight plates of the instruments employed at the Vesuvian observatory, and of views of the eruption in its different stages, which latter, however, as is frequently the case when taken from photographs, cannot be regarded as altogether satisfactory; the translation is done with evident care, but the nomenclature is open to objections, especially when such terms as sulphide of potash and ferrochloride of ammonia are encountered. The introductory sketch by which the translation is prefaced, occupies 90 out of 148 pages, and must be regarded as quite a distinct treatise, being only in The second part of this sketch is a résumé of the Vesuvius, on April 26, 1872, from a Photograph. I The Observatory.-2. Fossa della Vetrana. 3. Eruption of Smoke and Ashes, with Stones, from the Surface of the Lava. 4. The Novelle, St. Sebastiano, and Massa. 5. Lava which took the direction of Resina. 6. Lava which, from the Crater, took the direction of the Camaldoli 7. The Grain Stores, near Naples. 8. Resina. 9. Torre del Greco. 10. The Camaldoli. main features of Mr. Mallet's dynamical theory of volcanic energy, published in the Proceedings of the Royal Society for 1872, a hypothesis which explains volcanic action as originating in the secular cooling of our globe, when, to use the words of the abstract, "As the solid crust sinks together to follow down after the shrinking nucleus, the work expended in mutual crushing and dislocation of its parts is transformed into heat, by which, at the places where the crushing sufficiently takes place, the material of the rock so crushed, and that adjacent to it, are heated even to fusion. The access of water to such points determines volcanic eruption." To one who, like Mr. Mallet, assumes that heat, and heat alone, is in the first instance all that is required to account for the varied phenomena of volcanic activity, this explanation may appear satisfactory enough, although even if it be proved experimentally that the intensity of the heat thus produced in such cracks of contraction, or faults, as a geologist would probably term them, is sufficient to fuse the substance of the rocks in immediate contact, it would nevertheless be found even still more difficult to account for the quantity of heat requisite to melt up such vast volumes of rock matter as are known to proceed from volcanoes. Allowing, however, that even this difficulty can be satisfactorily explained away-and it is admitted that the conversion of the mechanical force into heat is sufficient to effect the melting part of the operation-there remains the still greater difficulty of explaining the chemi cal and mineralogical features which characterise volcanic phenomena. For although mechanical force is admitted to be convertible into its equivalent in heat, which heat may in its turn set in operation chemical action, still no such forces, either alone or combined, can transmute one chemical element into another, or bring about the formation of products having at all times a definite chemical and mineralogical constitution, out of the incongruous materials likely to be met with on the sides of such faults, or cracks, or contraction. Our present knowledge of the mineral characters of the earth's crust does not entitle us to entertain the supposition that the substance of the rocks immediately contiguous to fissures of this character occurring in so many different parts of the globe, could in all, or even in other than solitary instances, when fused by the action of mere heat, afford products identical with those of known volcanoes. On the other hand, nothing is more certain, from the examination of volcanic products, than that, no matter from what part of the world they be derived, whether from volcanoes situated near the north or south poles, in the islands of the Pacific or Atlantic oceans, or from the craters of the Andes or the Apennines, they are all identical in chemical or mineralogical constitution-a result which indicates forcibly that that they must be derived from some one common source, and not be mere local accidents, as Mr. Mallet's hypothesis would require us to assume. For these and other reasons which we need not bring forward on the present occasion, it does not seem probable that this hypothesis will receive the adherence of either chemist, mineralogist, or geologist. In conclusion, attention might here be directed to the disadvantages which, in a pecuniary point of view, the British student labours under when making himself acquainted with foreign science by means of translations. The original pamphlet of Prof. Palmieri in Italian, and its translation into German by the eminent chemist, Rammelsberg, were procured here in London for the small sum of eighteenpence each, whereas English translations of scientific works, got up, however, in superior paper, wide margin, and elaborate covers, can rarely (if ever) be obtained under several times the cost of the original works. DAVID FORBES OUR BOOK SHELF Human Physiology the Basis of Sanitary and Social Science. By T. L. Nichols, M.D. Pp. 479; woodcuts. (Trübner, 1872.) THE title "Human Physiology," which alone appears on the back of this book, is misleading, and even the title as given above would scarcely prepare a reader for what he will find. The preface, however, gives fair warning. "Physiology," writes Dr. Nichols, "the science of life, has been handed over to the medical profession, which has an unfortunate interest in the popular ignorance of sanitary laws; while metaphysicians, moralists, and theologians have confused rather than enlightened our ideas "as to the moral nature of man and his consequent social requirements." This seems rather hard on the doctors, who have certainly done all that has yet been done in preaching the laws of health and in getting them carried out, both by public supervision or compulsion and by private influence; but the whole volume is an exemplification of the latter part of the melancholy result, whether due to those designing persons who study metaphysics, morals, and theology or to some other cause. Dr. Nichols is an ardent advocate of the numerous theories which blind and bigoted Science has consistently and universally refused to accept, to the great disgust of circle-squarers, anti-Newtonians, popular "scientists," and Social-Sciencemongers. The first section of the book treats of preventible mortality, poverty, ignorance, drunkenness, and prostitution; the second of matter, force, and life, including adverse criticism, on the feeblest grounds, of the doc"proofs of immortality." The third part gives a popular trines of evolution and of materialism, with some remarkable account of the human body, with some of the oddest illustrations ever printed. The fourth treats of the laws of generation, including chapters on love and marriage, hereditary transmission, and problems of the sexual relation. This section is, perhaps, the best in the book, and its subjects are handled with freedom and modesty, while the conclusions are sensible enough. The fifth, part on health, disease, and cure, contains a good many useful and obvious remarks on the value of cleanliness, exercise, and temperance, together with a number of utterly unsupported or demonstrably false propositions. The last part, is devoted to the discussion of morals and society, in which important questions in political economy, ethics, agriculture, are stated, benevolent wishes for all classes of mankind are expressed, and the questions left much as they were found. In a book of this kind the reader is not surprised to encounter the old and new dogmas of phrenology, vegeanti-vaccination, and cure by Psychic force. But though tarianism, clairvoyance, homeopathy, animal magnetism, unscientific and sometimes anti-scientific, the author would deserve credit for putting before the public information which, however trite, is too little acted on, if his assertions of the wonderful cures he has made by hydropathy at Malvern, and the quotation from "a little book," by Mrs. Nichols on the same subject, did not suggest a doubt whether in his case singleness of motive can be admitted in excuse of ignorance. P. S. LETTERS TO THE EDITOR [The Editor does not hold himself responsible for opinions expressed by his correspondents. No notice is taken of anonymous communications.] Dr. Bastian's Experiments MR. LANKESTER asks me several questions relating to the experiments by Dr. Bastian, reported by me in NATURE a few weeks ago. In reply I beg to say that new Cheddar cheese was used. The cheese was not weighed, but the quantity added to the contents of each flask probably did not exceed two grains. The turnip infusion was filtered before it was introduced into the flasks: the filtrate was limpid. After boiling, the liquid was somewhat turbid, and contained visible particles. Feb. 3 J. BURDON SANDERSON Eyes and No Eyes MR. RAY LANKESTER'S letter has reminded me of a little I experiment of my own which converted me to Bastianism. had some turnip and cheese flasks which Dr. Bastian had been kind enough to prepare in my presence. I took them home and in due time examined the contents in a good microscope, using what I thought adequate power. I saw nothing, and went triumphant to Dr. Bastian to report my failure, taking the flasks with me. Dr. Bastian looked at the fluid, smelt it, and told me he would eat his hat if it was not full of life. I thought he would have to eat his hat. He put a drop under his microscope and told me to look. It was full of small Bacteria. I was a good deal puzzled at first, but after a little discussion I found out why I had failed to see what was in the fluid. Without going into details, I may say that the short result was that I had been rather a muff with the microscope. May not this explain some other failures ?— not Mr. Lankester's, of course. QUERY Meteor at St. Thomas THE enclosed reached me from a meteorological correspondent in St. Thomas. The records of such phenomena must be rare ; there may be something peculiar in this one; I therefore forward it to you. RAWSON RAWSON Government House, Barbados, Dec. 30, 1872 "On November 30, 1872, at 8h 10m P. M. a beautiful large meteor was observed, which passed from west to east with great brilliancy, and exploded in the zenith in numerous little stars. It lasted about three seconds. A little after a rumbling noise, like distant thunder, was heard. It is reported by the watch"man of the floating dock, which lies at present on the eastern beach of Long Bay in eight feet water, for repairs, that he was sleeping on the platform under an awning; he awoke from the heat and the strong light which passed close to him through the lattice work; and some ashes fell on the dock which he found but did not collect, not knowing that it was of value. As is well known, aerolites travel at the rate of 10,000 feet per second." Brilliant Meteor of the Antinomies does not answer, either, to Professor Clifford's Athenæum Club, Jan. 21 The Source of the Solar Heat Ir gave me great pleasure to find that Captain Ericsson has taken the same views as myself with regard to the Source of the Solar Energy; but there is a certain part of his article in NATURE, vol. vi. p. 539, which I do not quite understand. My views on this subject were sent to the Royal Astronomical Society, and were published in the Monthly Notices for April 1872, where it was easily shown that if E be the total energy destroyed in a given time by the crushing-in of the sun's massE = 8% Pors where g is the force of gravity at the sun's surface, r the sun's radius, LAST night about 10.0, the moment after leaving the room in which I had been lecturing, at Wordsley, near Stourbridge, the ground about me was lighted up as by the sudden flash of a near lantern or the emergence of the full moon from a bank of cloud. On looking up at the sky, I saw a rocket-like object shooting down with a slightly zigzag motion like that of a fish, and leav ing behind it a trail of mingled and mingling tints of green, purple, and yellow of nearly the semi-diameter of the moon. After a first thought about fireworks, I felt sure it was a meteor, and looked about for the constellations, so that I might be able to describe its path. The sky, however, was covered with clouds, only a star here and there being visible, and the moon, though easily seen, presenting a very hazy appearance. From inquiry at the Rectory as to the aspect of the schoolroom from which I had just come out, I judge that the course of the meteor must have been from north-west to west. When I first saw it, it was about 40° or 50° above the horizon, and it traversed about half the remaining space before disappearing, occupying, I estimate, about six seconds in doing so. Its path formed an angler, hence we may write of about 40° with the horizon. From the fact that the sky was covered with clouds and that the meteor illuminated the ground with a light superior to that of the "half" moon shining at the time, I judge that the meteor was between the clouds and the earth. This nearness, would, of course, be an element in its great apparent size (which would be added to by the zigzag motion); and as it would also prevent its being seen at great distances and by many observers, I have, after some hesitation, penned this record of my very imperfect observations. GEORGE ST. CLAIR London, Feb. 4 The Antinomies of Kant My attention has been directed by a friend to an address by Prof. W. K. Clifford, in Macmillan's Magazine for this month, containing a curious misrepresentation of Kant's teaching, and therein an instructive instance of ultracrepidism. The professor remarks: "The opinion that at the basis of the natural order there is something which we can know to be unreasonable to elude the process of human thought... is set forth first by Kant, so far as I know, in the form of his famous doctrine of the antinomies or contradictions, a later form of which I will endeavour to explain to you." "This doctrine," he continues, "has been developed and extended to the great successors of Kant, and this unreasonable, or unknowab'e, which is also called the absolute and the unconditioned, has been set forth in various ways as that which we know to be the true basis of all things." I am sure I should not be allowed, in the columns of NATURE, sufficient space to point out in detail the mi-apprehensions involved in these remarks. It is plain to me that Professor Clifford has approached the very difficult subject of Kant's Antinomies from the system of Sir William Hamilton. To start with Hamilton, however, is to be handicapped in the pursuit, and to augment the difficulties to be surmounted. In truth the doctrine Professor Clifford expounds is simply that of Hamilton; but Hamilton did not either develop or extend the Antinomies of Kant. He never understood them, but carved his little system out of a few splinters he gathered by the way. All Hamilton's characterisations of Kant are ludicrously false. This doctrine 20 the contraction of that radius in the given time; all corresponding to the present epoch. To find we must express E in thermal units by means of the dynamical theory of heat, and equate the result to the total amount of heat radiated by the sun; and it is easy to show that z must be 129 ft. per annum; and since Captain Ericsson finds the eontraction to be 121 ft., we are so far in agreement. But pr3 is the mass of the sun, and g, varies inversely as E=CZ where C is a constant, and R, Z, the values of the radius and or the contraction at any other epoch of time. Now there is no connection between Z and R; if Z varies as R2, then E is constant; if Z varies as R, which I believe to be the most probable assumption, then E varies inversely as R, and the total solar radiation must be slowly increasing; but I see no reason whatever for supposing that Z varies directly as R4, so that the solar radiation must be diminishing in proportion to the square of the sun's radius. MAXWELL HALL Jamaica The Twinkling of the Stars THE phenomenon observed and described by G. F. Burder in NATURE of Jan. 23, p. 222, does not, as I understand it, account in any way for the twinkling of stars, seeing that, by means of any two lights (gas lamps for instance) at the distance of a few hundreds of yards, the same effect may be observed, and this quite irrespective of the angle at which they are placed with reference to the horizon or the "blind spot" of the observer's eye. THOS. HAWKSLEY Meteorological Cycles THE following observation may possess some interest in connection with the subject of recurring meteorological cycles. It is found at the conclusion of Mr. Consul Wallis's report on the trade and commerce of Costa Rica for 1867, dated June 1, 1868 (Parliamentary Papers for 1868-69, vol. lix. p. 520):-"In the state of the public health there is a marked and satisfactory improvement to report. No reason can be assigned here for the large number of epidemic disorders which have afflicted this country for the last ten years and since the visitation of the cholera, nor for the improvement which took place in the eleventh year." R. G. London, Jan. 2 ON THE OLD AND NEW LABORATORIES AT THE ROYAL INSTITUTION* OF II. F the next great name connected with our Institution, namely, Michael Faraday, of his life and his discoveries the history has been already written, so far indeed as it can be written, by Bence Jones, by Tyndall, and by Gladstone. Si monumentum quæris circumspice. These volumes of notes, from 1831 to 1856, will give some idea of the amount of work which he did in our laboratory; and their value will be better appreciated through the consideration that before these notes were made, no less than sixty of his scientific papers had been printed, nine of them in the "Philosophical Transactions" Those of us who were present at Tyndall's two memorable lectures on "Faraday as a discoverer" are not likely to forget the impression of the man left by them on our minds; and for those who were not present it would be an office thankless to your lecturer and burdensome to his hearers, to contribute a feeble reproduction of those life-like memoirs, For our present purpose it will be sufficient to say that the entire fabric of those brilliant and manifold contributions to human knowledge was wrought out within the walls of the Royal Institution. His great experiments have been so often and so well exhibited in this theatre, that some apology is needed for bringing any of them before you again; but in repeating for my own instruction some of those which bear more particularly upon the subject of Light, I have been tempted to reproduce one of them here. In doing this I I have been perhaps moved more by a fascination of the phenomenon, and by a piece of instrumental good fortune which enables me to introduce an old friend under a new garb, than by any better reason. The experiment in question is that which Faraday called "the magnetisation of light, and the illumination of the lines of magnetic force;" we should now term it the rotation of the plane of polarisation under the influence of the magnetic field. And in order that we may not even by inadvertence confuse the rotation here produced with that due to quartz, or oil of turpentine, I will draw your attention, by way of memorandum, to the nature of the magnetism produced by spiral currents in given directions, and of the rotations of free currents produced by magnets. [The lecturer then showed the opposite rotations of two sparks discharged about the two poles respectively of an electro-magnet, and the reversal of those rotations, first by a change of the poles, and secondly by a reversal of the direction of the sparks.] You now see upon the screen an image of the figures produced by a magnificent piece of heavy glass under the action of polarised light. Its size enables me to make use of about four times the amount of light usually available in this experiment; and I have taken advantage of the figure which its imperfect annealing produces, to vary the effect upon the screen. The dark parts of the figure indicate the parts of the beam in which the vibrations are perpendicular to those transmitted by either polariser or analyser, and which are consequently cut off. Now if anything should intervene to change the plane of those vibrations a portion of them will be transmitted, and a partial illumination of the screen will ensue. This turning of the plane of vibration is effected by the magnet as soon as its force is developed by the electric current sent through its coils. [The lecturer then "dispersed" the dark lines of the figure by means of a plate of quartz; and after turning polariser and analyser so as to colour the centre of the field with the tint intermediate between red and violet (teinte sensible), he showed that when the magnet was excited the field was rendered red or green according to the direction of the poles.] • Continued from p 224 Professor Frankland before coming to us had isolated the compound radicals Methyl, Ethyl, and Amyl, and had proved their resemblance to Hydrogen. He had also combined them with the metals zinc, tin, mercury, and boron. By this means he had obtained a very powerful chemical reagent, which proved of eminent service in subsequent operations. An instance of its power will be found in zinc- ethyl, which by its rapid combination with oxygen of the air, bursts into spontaneous combustion as soon as a flask containing it is opened. In conjunction with Mr. Duppa, Prof. Frankland worked in our laboratory at the artificial formation of ethers. They treated acetic ether with iodine and with the iodides of methyl, ethyl, and amyl; and by their means they arrived at a method for the formation of many organic substances which had previously been obtained only through the agency of animals or of vegetables. In 1866 Dr. Frankland determined by a long series of calorimetric experiments the maximum amount of force capable of being developed by given weights of the different foods commonly used by men. In the following year he investigated the effect of pressure (up to 20 atmospheres) upon the luminosity of flames of hydrogen and of carbonic oxides. He found that these flames, so feebly luminous at ordinary atmospheric pressure, burn with brilliant light under pressures of from 10 to 20 atmospheres, and that the spectra of these brilliant flames are perfectly continuous. From the latter circumstance he infers that solar light may be derived from glowing gas and not from incandescent solid or liquid matter. As these researches have so important a bearing upon spectral analysis and solar physics, I will venture to repeat one or two of the experiments. Here are three closed tubes filled respectively with hydrogen, oxygen, and chlorine, at atmospheric pressure. The densities of these substances are in the proportions 1: 16: 35; and if the spark from an induction coil be made to pass through them, the luminosity of the discharge will be found to be nearly in the same proportions. That this result is really due to the density, and not to the chemical constitution of the gases, may be proved by allowing the discharge to pass through this tube, and by pumping air into it during the discharge. It will then be seen that the brilliancy increases with the pressure. These researches were suggested by an old experiment of Cavendish's, in which he exploded a mixture of oxygen and hydrogen, first under atmospheric pressure and then under a pressure of from 10 to 12 atmospheres. In the first case there is much noise and little light; in the second, a brilliant flash and no noise. The labours of Dr. Frankland have rendered this experiment intelligible, and have correlated it with other phenomena. Of Dr. Frankland's successor, Dr. Odling, I should have had more to say, had he not been attracted by a well-deserved offer of the chemical chair at Oxford. As a member of that University I rejoice at the appointment, while here we regret the loss. Of Faraday's successor, John Tyndall, I am greatly at a loss how to speak. In this place his presence seems so near to us, his thoughts so subtle, his words-even when rung back to us from those busy cities far away on the other side of the Atlantic-so familiar and yet so stirring, that it behoves us that ours should be wary and few. Few men have brought so large a burden and bulk of contribution to the common stock of knowledge; but still fewer have inspired in his hearers so strong a love, such ardent enthusiasm for the subjects of his research. It is now twenty years since Prof. Tyndall began his researches in our laboratory. During the first thirteen years he produced no less than thirteen papers, which were printed in the "Philosophical Transactions :" on Sound, on Diamagnetism, on Glaciers and Ice, on the |