In the discussion which followed the reading of Dr. Calvert's papers Dr. Charlton Bastian remarked upon the number of assumptions which were introduced, and gave reasons for his opinion that the experiments were wholly inconclusive in their nature. He was not aware that Prof. Tyndall had ever revealed an "abundance of germ life" in the air, whilst M. Pasteur had distinctly stated that he had been unable to recognise Bacteria or their germs in the dust filtered from the atmosphere. Even if Bacteria were widely diffused in the air, it would still have to be shown that they were alive. From the fact that some eminently inoculable fluids might be pretty freely exposed to the air for two or three weeks without showing the least signs of turbidity-though they could always be rendered turbid in two or three days after bringing them into contact with actual living Bacteria-he thought there was reason to believe that living Bacteria were by no means abundant in the air. And as he had found that all other naked lower forms of life with which he had experimented were unable to survive the effects of even short periods of desiccation, he thought there was much reason for the belief that the same rule would hold good for Bacteria. Dr. Bastian failed to find in Dr. Calvert's papers sufficient evidence that the organisms found in some of the solutions were really alive, and with regard to those experiments in which fermentable substances had been employed, it was assuming the very point at issue to suppose that the more numerous organisms which were present in them could only have come from the atmosphere. With regard to the influence of heat upon the life of Bacteria and many other organisms, Dr. Bastian gave some particulars concerning experiments, which tended to show, as he thought, conclusively, that they were all killed by an exposure in fluids, for ten minutes, to a heat of 60° C. (140° F.) There was no difficulty in ascertaining when Amoeba or Ciliated Infusoria were killed, though with respect to Bacteria there was much more difficulty. Where the movements were not of an active character, after the Bacteria had been subjected to different degrees of heat, no reliable opinion as to their life or death could be arrived at. Bacteria which were really living might in many cases exhibit movements differing in no respect from those which dead Bacteria would display. From the exhibition of such movements, therefore, it could not be positively affirmed that the organisms were living, or that they were dead. The case was different, however, with regard to reproduction-dead organisms could not multiply. Having found a fluid, therefore, which was most suitable for the nourishment of Bacteria, but which seemed to be wholly incapable of giving origin to them de novo, he inoculated portions of it with living Bacteria, and then found that those fluids which had been heated to 50° C. or 55° C. for ten minutes became quite turbid in two or three days, whilst others, heated for the same time to 60°, 65°, 70°, 75° C. and upwards, invariably remained clear and showed no signs of turbidity. As living Bacteria will always multiply under suitable conditions in suitable fluids, their failure to multiply was the best evidence that they had been killed. The conclusion that Bacteria were killed by exposure in fluids to a heat of 60° C. was one which had been previously arrived at by Prof. Wyman and M. Pouchet, though such a conclusion was now much strengthened by Dr. Bastian's recent experiments. These results were harmonious also with the fact that Amoeba, Ciliated Infusoria, and almost all the other lower organisms with which experiments had been made, were also killed by even a shorter expo. sure to a temperature of 60° C. (140° F.)

Geologists' Association, May 5.-Rev. T. Wiltshire, president, in the chair.-"On the Fauna of the Carboniferous Epoch," by Henry Woodward. In this paper the author protested against that mode of thought which seemed to imply that the globe was, during the various geologic periods, a vast aquarium, and urged the similarity of the conditions which now prevail with those that were obtained during the deposition of the various systems of the stratified rocks. Mr. Woodward combated the opinion of many, that during the Carboniferous period the atmosphere was heavily charged with carbonic acid gas, which, while it supplied the profuse vegetation of that epoch with carbon, prevented the radiation of heat from the earth, and thus produced an abnormal warmth which, with abundant moisture, was the cause of the vast growths that formed the beds of coal we now use for fuel. It was contended that the atmosphere under normal conditions was quite sufficient to supply all the carbonic acid that was required for the vegetation which composed all the beds in the world, and that, as we find the Gulf Stream exerting a

great influence on the climate of England at the present time, so unusual warmth and humidity and great alterations of the isothermal lines of the globe, might have been produced by ocean currents consequent upon changes of coast-lines and other causes of which we can know little. The animal life of the epoch was then described, and some valuable lists of species were appended to the paper. The Rev. Mr. Henslow, referring to Mr. Woodward's remarks respecting the discovery by Prof. Morris of the "Mother coal" of Bradford being made up of spores and spore cases, stated that Prof. Huxley had concluded that coal generally was formed in this manner. Prof. Morris heartily approved of Mr. Woodward's opinion in favour of the contemporaneity of formations usually considered to be of successive epochs, and pointed out the great differences in the thickness in the underlying beds, and in other stratigraphical conditions of the Carboniferous limestone, millstone grit, and coal measures, in various districts. In Shropshire, for instance, the Carboniferous beds repose upon Silurian rocks, and in Scotland the coal seams are intercalated with the main limestone. Mr. Woodward, after passing a high eulogium on Prof. Morris, whose knowledge of the subject was most varied and extensive, briefly described several species of crustacea of which diagrams were exhibited, and directed the attention of the Association to a cast of the head of an undescribed species of Anthracosaurus allied to A. Russelli, recently obtained by Mr. George Maw, from the coal measures of Coal

brook Dale.

cones.

PARIS

The

Academy of Sciences, April 10.-M. Chasles read a very interesting paper on the properties belonging to a system of Every one of these properties discovered by the law of analogy relates to a series of certain geometrical objects, com. pared with a series of other objects of the same nature. demonstrations are not given except by the arrangement of the different propositions, which are sixty in number, and fill twelve closely printed pages of the Comptes Rendus.-Dr. Declat, who does not belong to the Academy, read a memoir on the effects of phenic acid. He attributes to this specific the power of curing the German cattle plague, or at least of preventing it. The experiments do not appear, however, very conclusive.-M. Aubert presented a memoir on the moral causes of the inferiority exhibited by French armies during the last campaigning. These causes are very numerous, and the principal of them is the making of the army an instrument for the protection of an internal despotism. The discussion of these subjects was considered as being out of the limits and province of the Academy. The memoir in former years would have been rejected under the old rules, but the president, M. Delaunay, referred it to a special committee, composed of General Morin, director of the Conservatoire des Arts, and M. Amiral Paris. The Comptes Rendus for this sitting publishes a list of periodicals which were offered to the French Academy in the month of March. many as fifteen publications were special periodicals, which resumed their publication during the few weeks of the cessation of fighting round Paris. The celebrated Abbé Moigno has lost no time in starting his Les Mondes, as the whole set for March was presented to the Academy. The foreign list was very short and incomplete, as NATURE, which had been presented, was omitted. The only English paper mentioned was the Monthly Notices of the Royal Astronomical Society.-M. Barral, the editor of two agricultural papers which are mentioned in the aforesaid list-Bulletin hebdomadaire du Journal d'Agriculture and Journal de l'Agriculture-having taken steps opposed to Communist rule, was obliged to leave Paris. His papers are now published at Versailles. M. Wolf, an Austrian subject, was present at the sitting. He is conducting observations at the National Observatory, where the instruments were not packed as on the occasion of the former shelling and investment. They run the risk of being smashed to pieces.

As

April 17.-M. Payen read an important paper on Cellulose. It is known that stony fruits or stony parts of fleshy fruits, like cherries and peaches, are composed of cellulose, impregnated with incrusting materials. The digestion of this cellulose is rendered more easy and complete by giving to the animals some fatty matters. The same may be said of stems of vegetables and straw. The application of this theory to the breeding of cattle is obvious. M. Payen exhibited some reactions, which show theoretically that the results obtained in Germany by the analysis of evacuations are truthful and genuine. The paper

elicited some observations from M. Chevreul, who read after wards on his own account a short report on a small pamphlet written by him during the investment of Paris. The title of this brochure is somewhat long, and explains clearly the meaning of the work: "On a fault of reasoning which is committed very often by people engaged in natural philosophy when reasoning on the concrete. The explanations are drawn from the last writings of M. Chevreul." These writings are mostly communications presented by M. Chevreul to the Academy for the last three years, when he was strenuously advocating a new classification of sciences as well as of the different objects of nature.-M. Trécul read some interesting observations on the Vegetation of Ferns. -M. Sant Venant, a member of the Section of Mechanics, presented a paper written by M. Boussinerg, a promising young French mathematician, who does not belong to the Academy. The paper related to the observations of an immense number of transcendental equations which present themselves to the mathematical inquirer when studying physical phenomena.

April 24. The account of this sitting was published in the last number of NATURE. We have nothing of importance to add to it. All the Comptes Rendus of the period are signed by M. Elie de Beaumont, acting as perpetual secretary. M. Elie de Beaumont was formerly a senator, although it can hardly be said he has ever meddled with politics. M. Delaunay, the present director of the National Observatory, has inaugurated the regular publishing of a monthly abstract of meteorological observation. It is a practice which is revived from Arago's, but was stopped by M. Leverrier when he stepped into office in 1854.

BERLIN

Royal Prussian Academy of Sciences, March 6.-M. Roth read the continuation of his historical remarks upon the theory of metamorphism, and the production of crystalline slates. -Prof. A. W. Hofmann read papers on phosphuretted hydrogen, and on the direct substitution of the alcoholic radicals for the hydrogen in that compound.

March 9.-M. Riess read a paper on the action of the subsi diary currents of the electrical battery upon the main current and upon each other.

March 30.-Prof. Hofmann described an eudiometer with movable wires. The apparatus consists of a glass tube, with two short narrow tubes attached to it at right-angles, and opening into it opposite to each other; these are closed by steel caps, through which steel screws pass, bearing the platinum wires. The screws are furnished with loops for the attachment of wires. -Prof. Hofmann also read a memoir on isodicyanic æthers, com. pounds which occupy a middle place between the cyanic and cyanuric æthers; and another on biuret and allied compounds. Prof. Dove read a paper on the behaviour of agate in the magnetic field.

VIENNA

I. R. Geological Institution, April 18.-Prof. Peters, of Gratz, sent a communication about a newly discovered mineral spring at Hengsberg, near Gratz. Besides a large quantity of free carbonic acid and carbonate of lime, the water contains chlorine, bromine, traces of iodine, boracic acid, and among the alcalies a considerable quantity of lithium.-M. J. Pauer related a remarkable phenomenon which has occurred during recent years in the large lake of Neusiedel, near Oldenburg, in Hungary. This lake, which measured nearly six German (about 150 English) square miles, was entirely dried up in the year 1865, and the ground was gradually converted into arable land. During the last winter, however, the water regained its territory, and to the great damage of the cultivators the basin is again filled up nearly to the same extent which it occupied formerly. Documents were found which prove that similar events took place in former centuries, and on one spot were discovered trunks of trees root. ing in the ground as much as three feet in diameter. They prove that at a former period the lake was dry through a long series of years.-M. E. v. Mojrisovics presented a memoir on the so. called alveolaric Orthoceratites from the Triassic and Liassic deposits of the Alps. He proved that they all are the phragmocones of a particular genus of the family of the Belemnitidæ, and that their isolated rostra are the forms which Gümbel called Attractites. The genus was described many years ago by Fr. v. Hauer and named Aulacoceras, but he had united it with the

THURSDAY, MAY 25, 1871

education of the student intended for the medical profession, we should recommend it to be commenced while he is still at school, at the age of sixteen, by

II. THE TRUE FUNCTIONS OF THE SMALLER SCHOOLS

IN

N a recent article* we pointed out the prodigious waste of time and energy that results from the existence of no less than eleven medical schools in the metropolis, with from thirteen to twenty-one lectureships attached to each, and called attention to a scheme by which it is proposed that an amalgamation should take place between several of them.

It is maintained by those who have proposed this scheme that by its means a reduced number of central institutions would be created in which the preliminary subjects of medical education, such as natural philosophy, mechanics, rudimentary chemistry, and botany, could be taught in a much more satisfactory manner than at present, since the increased value of the lectureships would enable the lecturer to devote more time to their preparation, and to supply much greater wealth of illustration, whilst the larger number of students in attendance would correspondingly stimulate his zeal. At the same time the smaller hospitals and schools might still fulfil a very important rôle as supplying the means for the practical or clinical study of disease-certain lectureships still remaining attached to them.

The importance of good preliminary education in natural philosophy, taking it in its widest sense, for the medical practitioner, seems to us to be by no means sufficiently recognised. Up to a very recent time it has been almost entirely ignored. It is only within the last few years that any steps in the right direction have been taken by the great examining boards. Fifteen years ago the College of Surgeons required little more than a good knowledge of anatomy and the principles of surgery in those they admitted as members, and even now the acquaintance with preliminary subjects they demand is of a very rudimentary nature, as may be gathered from the fact that it includes only writing from dictation, arithmetic, algebra, geography, English history, the first two books of Euclid, and a little Latin translation, with one optional subject, which may be either Greek, French, German, mechanics, chemistry, botany, or zoology. We cannot but think that this programme might be advantageously extended.

Does it not stand to reason that the lad who is about to enter upon the study of Anatomy and Physiology ought to possess a competent knowledge of the principal facts of Natural Philosophy? How is he to comprehend the contraction of muscles, the action of the valves of the heart, the phenomena of respiration, the construction of the eye and ear, unless he is well grounded in Mechanics, already understands the lever and the pulley, and knows -the principles of Hydraulics and Pneumatics, the laws of refraction of light, and the conduction of sound? Nor can it be said that such knowledge is of temporary value only. The surgeon and physician must daily and hourly see cases which can only be treated properly by reference to such knowledge.

If we might venture to suggest a scheme for the * See NATURE, vol. iv. p. 1.

VOL. IV.

of London. The following year should be devoted to the study of Natural Philosophy, rudimentary Chemistry, and Botany; and there could be no doubt that these subjects could be admirably taught at all the larger and better appointed schools through the country. But these are precisely the subjects that might be taught to large classes in a most superior manner in the four or five institutions with which it is proposed that the smaller schools should be amalgamated. The preliminary examination, in which considerable knowledge should be demanded, might take place at the age of seventeen. In the following winter session the student, now thoroughly grounded, should begin the study of Anatomy and Physiology, and the following summer might be employed in pursuing Chemistry in its application to Medicine; Botany in the same relations; and the recently introduced subject of Practical Physiology; the first embracing such subjects as the chemistry of the excretions and secretions, &c.; the second, the orders containing medicinal plants, and the composition and formation of the vegetable alkaloids, &c. ; and the last, such points as the action of the valves of the heart, the processes of respiration and digestion, &c. The second winter session should be taken up in completing the knowledge of Anatomy and Physiology; and at the expiration of this session the first examination should take place, comprehending the subjects of Anatomy, Physiology, Chemistry, and Botany, the two latter points being at present almost wholly neglected. The second summer session might be occupied with the so-called Materia Medica, formerly merely consisting of the driest of all possible discourses on the composition and form of the various drugs, but with which our student is already perfectly familiar, and which might now be advantageously replaced by an account that could, in the hands of an efficient lecturer, be made deeply interesting, on the physiological action of drugs, and the effects of remedies on man and animals.

Up to the present time the whole work of the student could be conducted at one of the central institutions. From henceforward he might with great advantage be allowed to elect whether he would remain at this central institution, or go to one of the amalgamated

schools.

These might be made most serviceable as means of instruction in chemical medicine, surgery, and midwifery; and lectureships on these subjects, to avoid the loss of time to the students that would otherwise be involved in going to and fro, might be retained at the smaller schools. The instruction on these subjects would extend over the third and fourth winter sessions, at the end of which the final examination should take place. Thus it appears to us a vast improvement in the education of the medical student might be effected. He would enter the portals of his profession with a good general knowledge of the subjects he is about to study. The first years would be spent under circumstances in which he would obtain the best education on preliminary subjects the kingdom can afford, whilst the last two years would be spent under conditions in which the great field for clinical instruction possessed by the smaller hospitals could be

E

utilised to the utmost. This is, indeed, the special field which we look to the smaller hospitals to occupy in the future. Clinical instruction is pursued to a far greater advantage with a smaller than with a larger number of pupils.

M. TAINE ON INTELLIGENCE On Intelligence. By H. Taine. Translated from the French by T. D. Haye, and revised by the Author. Part I. (London: Reeve and Co., 1871).

IN

N a notice, some months ago* in these columns, of M. Ribot's clever exposition of English psychology, mention was made of M. Taine's work, De l'Intelligence, then newly come forth, as a striking evidence of the revival of French interest in the scientific investigation of mind. The first part of the work is now put before English readers in a translation satisfactory on the whole, and the second part is announced as soon to follow.

The first part, as readers of the original must be aware, easily admits of being published separately. This happens because M. Taine's exposition, while presenting in the detail all the best qualities of his admirable style, is in its main lines laid out with a strict regard to principles of logical method. It falls into two sharply marked divisions, an analytic and a synthetic. No explanation of the different heads of knowledge making up our intelligence is attempted, until, by an analysis expressly performed, the ultimate elements of human cognition are come at. Often our English works on psychology, while they pass for, or claim to be, analytic, and do contain many cases of special analysis, are, in strictness, synthetic; the foregone general analysis being kept out of sight, and its sufficiency being left to appear from the character of the explanation which its results, as brought forward, may be made to yield. Of this description are the works of Prof. Bain, and even James Mill's professed "Analysis." M. Taine, on the other hand, prefers to do his analysis not in the secret laboratory of his own mind but under the eye of the reader; and the operation takes up the whole of his first part here translated.

Obviously, when the phenomena are so complex and manifold as in the case of mind or intelligence, the analysis, if it is thus to be exhibited, and if it is to be brought to anything like a definite issue, must be of facts carefully selected for their illustrative or representative character; and this M. Taine well apprehends. Nor does he less clearly see that normal facts or events of consciousness no more suffice for psychological science than can everyday observation take the place of artificial experiment in physical science. At different stages, therefore, he looks about him for cases either of what may be called artificial mental action, as in the ingenious processes resorted to by mathematicians, or of abnormal mental action, such as the phenomena of madness, hallucination, &c., which are a sort of nature's experiments on a field where, for moral reasons, the freedom of experimenting is greatly limited. So, at the stage of the senses where experiment becomes perfectly feasible, he effectively turns to account the most advanced results got out in late years by psychologists or physiologists; and, again, at the last stage of the analytic sounding, when he strikes upon a bottom of bare physio* See NATURE, vol. ii. p. 331.

logy, he makes apt selection from the most recent experimental work.

He begins by resolving thoughts, or (in the strict philosophical sense of the term) ideas, into images, on principles of thorough-going nominalism. Ideas the least general are shown to be impossible as mental experiences, and to need representation by particular signs, and ideas the most general and abstruse are shown to come within the mental grasp still by signs or symbols. There is the difference that in the case of natural objects, like tree or dog, the substituted sign, generally a name, is the direct expression of a mental "tendency" arising under actual impressions, varied at the same time that they are similar; while to conceptions like those of mathematical science there may correspond no distinct impressions, and the sign is struck out according to an elaborate system of indirect substitution-substitutions upon substitutions. But always some definite image is present to the mind. The question, then, is to investigate the nature of particular images; and, by a very instructive muster of normal and abnormal instances, the laws of their retention out of consciousness and revival in consciousness are brought out, with the result that the image is itself seen to be a substitute of sensation below it. Must the analysis then end in a mere description of the kinds of sensation, with account taken of physical conditions? M. Taine thinks it need not, and wisely selects for special inquiry the sensations of sound-wisely, not merely because Helmholtz's classical investigations lie ready to the psychologist's hand, but also because no other set of sensations is at once so varied in character and so free from admixture with extraneous elements. The result thence obtained, confirmed more or less from the senses of sight, smell, and taste, and not contradicted by the sense of touch, is that all qualitative differences of consciousness within each sense are explicable as different compounds of an elementary sensation not conscious; such elementary sensations, different in the different senses, being further conceivable as themselves developed by composition out of a single infinitesimal " event," of course imperceptible to consciousness, the truly ultimate element of all that appears as mind. But in relation with this there will stand a molecular displacement in nerve; for, as the physiological analysis, taken up when the psychological reaches its term, finds in the sensory ganglia the seat of crude sensation, and in the cercbral lobes with their cortical layer a "repeating and multiplying organ" through which sensations are associated and revived as images, and thus become knowledge, so it may see in the reflex action of lower nerve-centres the physical correlate of the simple unconscious "events" or elements of sensation. And thus the complete analysis of intelligence discloses two worlds, the moral and the physical, in mutual correspondence down to the lowest depths of human nature, and, by analogy, to the very foot of the zoological scale.

Save that M. Taine's method of procedure is his own, and his expression is always striking, there is little thus far in which he has not been anticipated by one psychologist or another among ourselves, notably by Mr. Spencer in the resolution of sensation. Nor in breaking up, in the last chapter of this part of his work, the metaphysical entities self and matter, regarded either as substances or as systems of faculties and forces, does he do more than

follow the English authorities, as they follow their great master, Hume. But in giving final expression to the relation between the two series of "events," psychical and physical, shown by the analysis to be involved in the varied phenomena of intelligence, he is more strictly original; or, at least, his view is stated with peculiar neatness and force. How shall sensation, whether in the crude form or in the intellectual condition of the image or in the elemental state, be conceived as joined to something so disparate as a molecular movement in nerve: that is the difficulty. To say that what we have united is rather an idea of sensation had by (or, in the case of the ultimate psychical element, conforming to the type had by) direct personal consciousness, and an idea of nerve got indirectly by way of external sense, though this is philosophically true, touches the difficulty without removing it; for the two ideas are still irreducible to each other. But it may then more readily be suspected that the "events" are not two, but one, with two permanently distinct faces to cognition; and this, in M. Taine's view, is the final outcome of the analytic, though as regards the duality he hints at a possible reduction in his second part. Meanwhile, taking the physical aspect as secondary and the sign of a properly mental event, he seeks to illustrate the view and to enforce his theory of universal correspondence by a remarkable analogy. He supposes an original text with an interlinear translation; the translation plain and legible at the outset, but becoming confused farther on, and before the end no longer to be made out; on the other hand, the text very clear at the last but fainter higher up, and about the beginning not to be traced at all. The writing may represent nature; clear text and undecipherable translation mark the states of full intellectual consciousness so vaguely referred, at least in detail, to the complex of the brain; faint text and translation not too plain mark the cruder mental events referred to less but still highly complicated centres; finally, visible translation and blank instead of text mark the well-ascertained physiological phenomenon of reflex action, for which it is as legitimate, if not necessary, to suppose a psychical obverse, albeit unconscious, as it is to assume for highest consciousness a physical correspondence in brainprocesses eluding our finest observation.

The analogy is instructively worked out further by M. Taine; but enough for the present. Another time we may better estimate the value of parts of his analysis, when considering how, from the materials it affords, he is able to build up the edifice of human knowledge.

G. CROOM ROBERTSON

A STORM-ATLAS FOR NORWAY

Storm Atlas of the Meteorological Institute of Norway. (H. Mohn.)

A KNOWLEDGE of the laws which regulate the progress of storms would be of comparatively little practical interest without the telegraph, but, since the speed of electricity outstrips that of wind, the information by telegraph that a storm has appeared at an outpost may be of great importance to a maritime country like our own, provided we know the path which the storm is likely to pursue.

Of late years practical meteorologists have devoted a great deal of attention to this branch of their subject, and the memoir before us is not the least interesting of the various contributions which have been made. It is unnecessary to enter into the details of M. Mohn's observational system; let us rather invite attention to the general conclusions at which he arrives.

"Barometric maxima," he tells us, "often remain during a considerable period over the places where they have been formed, while, on the other hand, barometric minima are almost always in motion over the surface of the earth, transporting themselves (in Europe) almost always towards the east." He further finds that the barometric minima represented in his charts have their greatest velocity of motion before they arrive at the west coast of Europe, and a smaller velocity when they pass by Scandinavia; in Russia the velocity is again greater.

As regards the component of the movement which leads the centres towards the east, he finds a greater regularity exhibited, inasmuch as this component diminishes continuously as the minima move from the sea towards the interior of the continent. The curved paths of these minima are at north Europe sometimes very regular and sometimes very sinuous; in general they are concave towards the south. The mean movement in the direction of the meridian is towards the north in the Atlantic ; towards the south, but feebly, in Scandinavia; and more strongly towards the south in Russia; in this latter country they appear to lose themselves.

Charts

Let us now invite attention to the following remarks of the author with regard to vapour :-" Vapour tension is an element of which the importance for the theory of tempests was not so evident to me until I had commenced the construction of these charts. giving the relative humidity are without any value, nor do they present any trace of that continuity which shows itself so strikingly in the charts of vapour tension." Further on he says:-"I have frequently remarked in this memoir that watery vapour is one of the most important elements in studying the movement of air; it is therefore much to be desired that the publication of meteorological observations should embrace vapour tensions (which is not always the case), and if only one element can be given, let it be rather that than the relative humidity. Charts representing the distribution of the vapour of water over the surface of the earth analogous to the temperature charts of M. Dove or the isobaric charts of Mr. Buchan would be of the greatest possible utility."

It may not be out of place to make a few remarks upon these observations of M. Mohn. Meteorologists have been in the habit of discussing in two ways the state of the air with regard to vapour. They have in the first place studied the vapour tension present in the atmosphere, and secondly, they have studied the relative humidity, or what M. Mohn calls "l'état hygrométrique." This latter element, representing the proportion between the vapour actually contained in the air and the full amount due to the present temperature, is an element that varies very greatly with the temperature, and is, therefore, of comparatively little use in meteorological researches.

Besides these two elements, the author of this review has suggested the hygrometric quality of the air as a