nished to twenty grains; and in three days more the patient was cured.

Cholera Morbus.-An incalculable number of letters, memoirs, and documents of every description, have been piled on the table of the Academy relative to the cholera morbus; but as they generally consist of speculative theories, and merely controversial discussions, it would be idle to lay them before our readers. An exception, however, to this rule exists in a paper forwarded by Dr. Jahinichen, who, as a member of the council appointed to examine the progress of the disease, had personally observed the majority of cases in Moscow, and whose talent renders his opinions valuable. The conclusions at which he has arrived are the following:-1. The cholera morbus is not a pestilential disease. 2. It is not either directly or indirectly contagious. 3. A germ or miasma of cholera emanating from the diseased person exists in the atmosphere surrounding him. 4. These emanations may be sufficient to originate disease, even when only proceeding from a single person, if the malady be violent, but will always be so in a hospital. 5. But a particular predisposition (arising generally from the greater or less irregularity in the mode of living) is necessary in each individual, to produce the developement of this miasma of cholera. The proportion in which this predisposition exists in a population has not been ascertained with sufficient certainty to establish a general rule; at Moscow it was about three in every hundred. 6. The propagation of the cholera is in accordance with the usual laws of epidemic diseases. 7. There is every reason to believe that pulmonary absorption is the only method by which the miasma is introduced into the human body. There is, therefore, no contagion, in the strict meaning of the word, but rather a species of penetration. 8. The miasma appears to have a peculiar affinity with the aqueous vapours in the atmosphere, and to be equally volatile. Dr. Jahinichen then adds, that he obtained, from the condensation of these vapours in rooms containing a number of patients, a substance entirely resembling that obtained by Moscati at Florence, and suggests that a close observation of the hygrometrical and barometrical variations of the atmosphere may throw light on the geographical march of the disease. He also thinks it probable that the miasma inherent in the aqueous vapours may rise in the atmosphere, and, being transported by a current of air to other countries, be inhaled by the inhabitants of those countries, and thus originate the disease. Should this conjecture be well founded, all quarantine and other precautionary measures must be useless, unless respiration could be suspended; and there is reason to fear that the ravages of the disorder in the western parts of Europe may be more extensive than in Russia, in consequence of the prejudices existing against hospitals, which, by keeping the patient at home, will render each house a separate source from which the fatal

miasma may emanate. We should mention that these opinions of · Dr. Jahinichen have been warmly attacked by M. Moreau de Johnes, and other advocates of the contagious properties of the disease, but their arguments are rather theoretical than founded on specific facts.

NATURAL PHILOSOPHY.

Electrical relations of bodies to heat.-At the meeting of the Académie des Sciences, held on the 17th of January, M. Becqueril read a memoir entitled 'Theoretical considerations on the changes operated in the electrical state of bodies, by the action of heat, contact, friction, and different chemical actions, and on the modifications which are occasionally produced in the arrangement of the constituent parts of those bodies.' The object of this memoir is to explain some of the causes which in process of time effect a change in many of the substances forming the superficial stratum of the globe. After referring to Laplace's theory of the igneous origin of the earth, he observes, that the diminution of the temperature must have successively produced great change in the combination of the elements of which the bulk of the earth is composed, in the constitution and pressure of the atmosphere, &c. He proposes to trace the origin of all these phenomena, and to investigate their causes and physical laws, and commences by some general cousiderations on certain properties of matter; after which he examines the effects of heat on the electric fluid of metallic substances considered separately and in contact, and the state of the atoms in the various combinations. By means of a very simple apparatus, he demonstrates that heat does not possess any influence over free electricity; but on the contrary acts very decidedly on the natural fluid. He has observed, that the heat which separates the molecules of bodies, produces on the natural fluid an effect analogous to that obtained by the cleavage of regularly crystallized substances, viz. the diminution of the reciprocal action of the two electricities. He then enumerates a variety of experiments, which authorize the conclusion, that the two electricities are raised by heat to a higher : degree in bodies which are negatively than in those which are positively electric. This fact explains the reason of the oxides of the negatively electric metals being more easily decomposed by heat than those of other metals. He then, after having given a detailed account of the various phenomena relating to the influence of heat in exciting the electric power in metals, enters into the question of the development of electricity by contact. Volta, in attacking Galvani's theory on muscular contractions, conceived the idea that they were owing to the electricity emanating from the contact of two heterogeneous substances: according to his theory, two substances always become in a state of contrary electricity by mutual contact, leaving out of consideration any modifications produced on the surfaces in contact. M. Becqueril then noticed the theory,

advanced by M. Delarive in opposition to Volta, that the action of the contact was only the result of the difference of the chemical actions of the air and water, and of external agents, on each of the two bodies; and stated, that though he had at first been staggered by it, the consideration that the electric fluid acts as a moving power in producing combinations induced him to retain his original opinion. In order to show the nature of this action in its full extent, he pursued his experiments on mineral substances which are electric conductors, and so little susceptible of atmospheric action, that their constitution sustained no change from being exposed for ages to the inclemency of the seasons. He details his experiments on platina, peroxide of manganese, magnetic oxides of iron, and gold; from which it appeared that the peroxide of manganese was, as might be expected from its high degree of oxydisation, negative in its contact with all the other bodies. He next examines the causes of the thermo-electric action in closed circles composed either of one or of two different metals, and states, from all his experiments it appears that these phenomena are owing to the difference of the thermo-electric powers of the metals. From some observations made on the relation between the thermo-electric faculties, and the capacity for heat in various metals, it appears that those metals which are most negatively electric have the least specific heat. The memoir concludes with an exposé of the electric properties of atoms. M. Becqueril examines the theory of M. Ampère, and also that of M. Bégneul, who, from the experiments he had made, concluded that the atoms in combination were merely small electric piles, the reciprocal and continuous action of which constitute what we call molecular attraction; but M. Becqueril considers the question, whether the action of particles of bodies on each other is entirely produced by electric action or by some unknown power, as still undecided.

ZOOLOGY.

Sturgeon.-On the 24th January M. Cuvier made a very favourable report to the Academy on a work by Messrs. Brandt and Ratzeburg, of Berlin, entitled the Monography of Sturgeon, in which the genus is divided into fourteen species, which are described with great minuteness, and in a manner calculated to be of great advantage to zoologists.

Teleo-saurus. On the 21st February M. Geoffroy de St. Hilaire presented his two memoirs on the animal, the fossil remains of which were discovered in Normandy in the years 1828, 1829, and 1830, which has been erroneously designated as the fossil crocodile of Caen. He now names it the genus teleo-saurus. These memoirs describe, at great length, the difference between this animal and the crocodile: the scales have no centre ridge, but are placed one over the other like those of fish, whence it is supposed that this animal was more

essentially aquatic than the crocodile. The whole of the animal has been now found, with the exception of the anterior feet and part of the posterior feet. The whole plastron of the back of the teleo-saurus is not composed as in the crocodile of several rows of plates careened to the centre, but of two rows only of plates without apparent projecture, the outward part thin, and the inner, by which they are strongly united together, very thick; they cover each other behind like the scales of fish. The fore part of the tail is also covered with two rows of scales only, but these present a longitudinal ridge towards the outward part, which forms two projecting lines, which gradually approach each other towards the hinder part. The back part of the tail, which answers to the crest (crête en scie) of the crocodile, has but one row of orbicular plates, which are strongly careened at the centre. The lower plastron exhibits six transverse rows of scales, which are not flexible like those of the crocodile's belly, but all strong and solid, whence the whole plastron could only be moved in one piece. Thus, in the general movements for the purpose of introducing the air into the lungs, the action of the two plastrons is similar to that of the two parts of a bellows. M. de St. Hilaire stated, that from the fact of the posterior aperture of the nostrils being situated at the middle part of the cranium, he had been induced to imagine that the mode of respiration of this animal must have been more nearly allied to that of the tortoise than of the crocodile-a supposition which is fully confirmed by the construction of the plastrons. It appears (in confirmation of the aquatic nature of the teleo-saurus) that its posterior members must have been at least double the size of the anterior, resembling the kangaroo in its mal-adaptation for walking; while the manner in which its whole body was closely covered with scales prevented its having the agility in leaping of that animal, so that it was only adapted for the water.

Two-head Lizard.-At the meeting of the Academy of the 28th February, M. Beltrami announced, that in a recent excursion over the Pyrenees, he found a two-headed lizard, with five paws, four of which were naturally formed, but the fifth, which was placed between the two heads, had nine toes. M. Beltrami promised to furnish the Academy, on a future occasion, with a minute account of the habits and mode of life of this animal.

ANALYSIS OF BOOKS, AND SELECTIONS FROM THE TRANSACTIONS OF SCIENTIFIC SOCIETIES.

The Life of Sir Humphry Davy, Bart., LL.D., late President of the Royal Society, &c. &c. &c. By John Ayrton Paris, M.D., F.R.S., &c. &c. 4to. London, 1831.

(Concluded from p. 360.)

IN the year 1808, MM. Gay-Lussac and Thenard succeeded in decomposing potash by chemical means; and Davy soon repeated their experiment. This process afforded the means of procuring potassium more readily in larger quantities than by means of voltaic electricity. The facility of the combustion of the alkalies, and the readiness with which they decomposed water, offered Davy the ready means for determining the proportions of their constituent parts he thought potash composed of about six parts base and one of oxygen; and soda, as consisting of seven parts base and two of oxygen. The over-excitement and fatigue of his researches upon this occasion, and the irregularity of his habits, threw him into a fever. Such was the alarming state of his disorder, that for many weeks his physicians visited him four times a-day.

The course of lectures on Electro-Chemical Science, which he gave on his recovery, commenced in March, 1808, and the theatre of the Institution overflowed with admiring and interested auditors. At the same period he gave a course in the evening on Geology, which was equally attractive. Having succeeded in decomposing the alkalies, it was natural that he should turn his attention to the earths; he, however, found them much more

difficult to conquer. While busily engaged in pursuit of his object, he received a letter from Professor Berzelius, of Stockholm, announcing that, in conjunction with Dr. Pontin, he had succeeded in decomposing baryta and lime by negatively electrising mercury in contact with them, and by such means had actually obtained amalgams of these earths. Davy immediately repeated the experiments with success; and having, by additional experiments, fully established the nature of these bodies and the analogies he had anticipated, he published the result in a memoir to the Royal Society in June, 1808, entitled- Electro-Chemical Researches on the Decomposition of the Earths; with Observations on the Metals obtained from them, and on the Amalgam of Ammonia.'

It has, however, been doubted whether the change, which ammonia and mercury undergo by voltaic action, merits the name of amalgamation, and whether it may not be referred to a purely mechanical cause; and Dr. Paris observes, in a note, that this opinion is strongly confirmed by Mr. Daniell's paper On certain Phenomena resulting from the action of Mercury upon different Metals,' published in the first number of this Journal.