REPORT ON THE TRANSACTIONS

OF THE

SOCIETY OF PHYSICS AND NATURAL HISTORY OF GENEVA,

FROM JULY, 1863, TO JUNE, 1864.

BY DR. CHOSSAT, PRESIDENT.

TRANSLATED FOR THE SMITHSONIAN INSTITUTION.

In conformity with article 7 of our laws, I am about to present to the society an account of its transactions and its progress during the year in which I have had the honor of being called to preside over it. The society, I regret to say, publishes no special bulletin of its sittings; the annual report of the president, at the close of his official term, is intended to supply its place. This, however, it can only do imperfectly, because, from the necessarily tardy date of its publication, some of the results communicated must have partially lost the character of finality. However this may be, the greater portion of the labors of the year have been successively inserted either in the present volume of memoirs, or in the archives of the physical and natural sciences of the Bibliothèque Universelle; so that my task to-day will be limited to a concise recapitulation of those labors. Since the end of September last, the society has been deprived of the special collaboration of our excellent colleague, Professor Claparède, whose infirm health has obliged him to withdraw from the functions of secretary of our sittingsfunctions which for many years he discharged in so distinguished a manner. His place has been filled, provisionally at first, by MM. Alexander Prevost and de Loriol; and definitively since, by M. Alexander Prevost alone, whom you designated for this office 21st January last. Such has been the obligingness of these gentlemen, and so clear and detailed their report of the current proceedings of the society, that the execution, always more or less difficult, of my present duty has been facilitated to the utmost possible degree; and I shall be permitted, I am sure, to present to them, as well in the name of the society as my own, the most sincere acknowledgments.

Agreeably to the usage adopted in former reports, the present account will be divided into two principal parts: that of the physical and that of the natural sciences; parts which will be then subdivided into as many special sections as the nature of the communications made to the society may prescribe. In each of these sections we shall speak, first, of the original memoirs which have been read; and next, say something of the verbal reports which have been made to the society during the year. We commence with astronomy.

PHYSICAL SCIENCES.

ASTRONOMY-Memoirs-M. Emile Gautier read two memoirs on the constitution of the sun. With M. Kirchhoff, he regards this body as a globe in fusion,

incandescent, and surrounded with a vast atmosphere; he conceives that this atmosphere, constituted chiefly of thick and metallic vapors, must be incomparably more dense than the terrestrial atmosphere, and he attributes to it the protuberances and roseate border observed in total eclipses, as well as the dappled appearance of the surface of the sun. But he denies to it the action attributed by M. Kirchhoff in the production of the solar spots.

As regards these spots, M. Gautier considers them to be connected with oxydations, with masses of salts and scoriæ, with solidifications, in a word, which are temporarily formed on the surface of the sun; and this, under the influence of exterior refrigeration or interior chemical action, in much the same manner as is observed in great masses of metals in fusion, in our industrial operations. The author admits the results of M. Sporer and those of M. Carrington regarding the apparent differences in the duration of the rotation of the sun, according to the heliographic latitude of such of the spots as are adopted for the calculation of this rotation. And in reference to the acceleration in longitude of the points of the equatorial zone, he considers it, with our colleague M. Cellerier, as resulting from the action exerted upon the solidified masses floating on the surface of the sun, whether by the friction of the heavy and metallic atmosphere of that orb, or by the interior rotary movement of the strata of its mass in fusion. These two components being both a function of the velocity and of the cosine of the latitude, (though this cosine has a different power for each of the two components,) they vary with each parallel, and their resultant may supply the reason of the acceleration in question. For the rest, although the author does not consider the mean density of the sun to be inferior to that of water, yet he admits that its low degree of density might form a serious objection to his theory of the spots, an objection which will be met on his part by a deliberate and thorough examination.

Professor Plantamour read us an extract from a very interesting memoir on the horary and telegraphic operations, by means of which the longitude of the observatory of Neuchâtel has been connected with that of the observatory of Geneva. These operations have led to some new results on the employment of the telegraph in determinations of this nature. But, as the paper of M. Plantamour appears in the present volume of the collection of our memoirs, we confine ourselves to a simple mention of it. The same physicist presented a note on the rectifications to be applied to the general system of levelling for Switzerland, and on the choice to be made, as a point of departure above the sea, between the mean level of the Mediterranean at Marseilles and the mean level of the ocean, as the latter results from very exact measurements executed in nineteen of the principal ports of France between Bayonne and Dunkirk. M. Plantamour would prefer the level of the ocean, the mean of which is 0.80 higher than the mean level of the Mediterranean at Marseilles.

Verbal reports.-Professor Alfred Gautier presented statements, full of interest, on several astronomical labors executed in different observatories of Europe and America. These statements bore more particularly, firstly, on the spots of the sun, their reciprocal occultation observed at Altona, and their presumed connexion with the aurora borealis and magnetic variations; likewise, on the two periods, one of eleven and the other of fifty-six years, recognized by M. Wolf in the number of these spots; secondly, on the photometric researches of M. Alvan Clarke, relative to the intensity of the light of the sun compared with that of the fixed stars; whence it would result that our sun cannot be one of the brilliant stars of the heavens; thirdly, on a slight augmentation to be applied to the value of the parallax of Mars as hitherto recognized, an augmentation which would imply that our distance from the sun is a little less than that at present admitted; fourthly, on the observation of shooting-stars by P. Secchi, from which it results that these meteors are situated at a height of 100 to 150 kilometres, and hence that they are within the limits of our atmosphere; fifthly, on

the lines of the solar spectrum, which, at an elevation of four miles above the ground, remain identical with those on the surface of the earth, only the spectrum diminishes in extent in proportion to the elevation attained; sixthly, on the discovery of a satellite of Procyon; on the light of of the Ship, which, in the space of twenty years, has passed from the first to the sixth magnitude; and finally, on a deviation of 10" of the plumb-line in the environs of Moscow, at a distance from any description of mountain.

METEOROLOGY.-Memoirs.-The great and valuable labors of our future president, Professor Plantamour, on the climate of Geneva, pertain by peculiar right to our society, and would have occupied a distinguished place in the collection of our memoirs, if their extent had not compelled the author to have them printed and published separately. This work, one of true scientific importance, inasmuch as it is based on observations executed with improved instruments, and repeated every day and several hours of each day for thirty-five consecutive years, and finally discussed with all the resources of modern science, could not be analyzed in a report necessarily so much circumscribed as the present; besides that, it would now be the more useless to attempt such analysis, since Professor Aug. de la Rive has recently given, in the archives of the physics and natural sciences of the Bibliothèque Universelle, a detailed and highly interesting account of the enterprise.

Verbal reports. Professor Plantamour communicated some of the results obtained during the month of January last, at the meteorological stations of the valley of the higher Rhone. Some singular anomalies of temperature have there been realized. Thus, among others, it was found that it was colder at the village of Rechingen (valley of Conches) than at the hospice of Saint Bernard, though the latter is situated 1,140 metres higher than the village. These anom- ♦ alies may be explained sometimes by the presence or absence of the sun, and sometimes also by the cold air flowing from the mountains and accumulating gradually in the bosom of the narrow valleys. Professor Marcet informed us of the results of M. Glaisher on the diminution of the temperature of the air in proportion to the elevation attained-results gathered in England and by means of balloon ascensions. The diminution is not regular, most probably from circumstances purely accidental, such as momentary currents of cold air, or enormous strata of vapor, which arrest the solar heat and reflect it toward the higher spaces. After traversing cold mists of some thousands of feet in thickness, M. Glaisher found at 11 or 12,000 feet of elevation the same temperature as at the surface of the earth. Professor Wartmann reports, in relation to atmospheric electricity on high mountains, that it had been observed this year in an ascension of the Jungfrau, as had been done the year before on the Diablerets, that at the approach of a storm the ironed staves of the tourists commenced intonating, and that singular sounds were heard in the air. Professor Gautier spoke of torrents of 1ain having fallen in Italy, in February Jast, accompanied, at Rome, by a furious hurricane, which transported thither sand entirely similar to that of the desert of Sahara. Professor Marcet remarked upon the relatively very mild temperature of the winter of 1863-64, in Canada, a fact which navigators believe they account for by a change observed, as they suppose, in the direction of the Gulf Stream. M. Chaix read to us a report on the results of late travels in Arabia, and particularly those of Palgrave, who succeeded in traversing the country by passing for a Syrian.

MATHEMATICAL AND EXPERIMENTAL PHYSICS.-Memoirs.-M. Ch. Galopin read an extract of a memoir on the mathematical theory of double refraction. After reciting the principles on which rests the theory of Fresnel, and having indicated the process followed by that eminent physicist for applying analysis to transcendental researches, our colleague adopts as his own the views of Cauchy, who regards the movement of light as a particular case of the movement of a system of molecules, very slightly diverted from their position or equilibrium,

and solicited by mutual forces of attraction and repulsion; and he gives the dif ferential equations, whose integration would furnish the value of the molecular displacements. By a method peculiar to himself, M. Galopin, with the help of certain artifices of analysis, arrives at the equation of the velocities of luminous waves already given by Fresnel, an equation which may be regarded as representing a surface called that of elasticity, and from which he deduces the equation of the surface itself of these waves. Besides the two surfaces in question, there still exist six others, the study of which enables him to arrive rapidly at the properties of the surface of the waves, at those which concern the peculiar points and planes of that surface, the conic and cylindrical refractions, and finally the ordinary and extraordinary rays of crystals of two axes.

M. Lucien de la Rive has made researches on the differences of density of a gaseous mass revolving around an axis in a cylindrical vessel, and has arrived at a formula which enables him to calculate these different densities. The differences in question are little appreciable for volumes of gas and dimensions of vessels of inconsiderable quantity; but they increase in proportion as the diameter of the vessels is larger. The last named physicist read a memoir on the conductibility of ice for heat. After having given the detail of his experiments, he recapitulates them mathematically, and proceeds to deduce to the value of the co-efficient k, of the conductibility of ice, a co-efficient which he finds =0.25, that of glass being 0.13, and that of porcelain 0.24. Then applying his results to the formation of ice on a surface of water below 0°, he seeks for the law according to which this formation takes place, and he arrives at three equations corresponding to three different epochs of the formation in question. Now, as the last of these equations is that of a parabola, he thence deduces that after the lapse of quite a few days of frost, the ice can only increase very slowly. The author finally establishes the agreement of his theory with known facts, with the observations of Flauguergues particularly, and concludes by indicating briefly the application which may be made of it to the formation of the polar ices.

Verbal reports.-Professors Wartmann and Marcet, in several successive verbal communications, brought to the notice of the society the interesting discussion in progress between MM. Magnus and Tyndall, on the absorption of heat by gases. M. Tyndall, in repeating his experiments without employing the diaphragm of rock-salt, has removed one of the most serious objections of M. Magnus. From his results he derives consequences of importance for the theory of Wells on dew, and for other atmospheric phenomena. Professor Marcet made the additional remark that Dulong, in his investigation regarding the specific heat of gases, had set out with the hypothesis that gases do not radiate; now, since M. Tyndall has established that they do radiate, the results of Dulong would seem to call for revision, account being taken of the radiation. Professor Plantamour occupied our attention with the views of M. Hipp respecting the establishment of electric clocks in cities. Their employment at Geneva has greatly conduced to a determination of the conditions by which their disposal should be governed. Their position in gas-lanterns exposes them to great variations of temperature from summer to winter, to the unfavorable influences of dust and humidity, and to the disturbing effects of the discharges of atmospheric electricity and of concussions produced, whether by gusts of wind or the frequent washing of the lanterns-concussions which have sometimes caused temporary loss of the current. By reason of these difficulties, M. Hipp would prefer that such clocks should be placed in the wall of the fronts of houses rather than in the gas-lanterns. M. Philip Plantamour presented an analysis of the researches of M. Edlüng on the formation of ice in the northern seas. According to the latter, the sea begins to freeze from the bottom; the water being there cooled below the point of congelation, the least shock, the passage of fish for instance, suffices to determine solidification and to produce the sudden formation

of masses of ice more or less considerable, which rise and float on the surface of the water. The analysis of M. Plantamour has been inserted in the Archives of the Bibliothèque Universelle.

CHEMISTRY.-Memoirs.-Professor Marignac communicated to the society the continuation of his researches on the silico-tungstates. He has recognized three distinct acids formed by the combination of tungstic acid and silicic acid, namely: 1st. Silico-tungstic acid, containing 12 equivalents of tungstic acid for 1 of silicic acid; 2d. Silico-decitungstic acid, 10 equivalents of tungstic acid for 1 of silicic acid; 3d. Tungsto-silicic acid, which has the same composition as the first, but which differs by its crystalline form. He remarks that a great number of salts of these acids present crystalline forms almost identical, although not by any means so in their composition. This fact seems to him to indicate the necessity of admitting the following extension of Mitscherlich's principle of isomorphism, viz: that two compounds including an element or a group of common elements, which constitutes by much the greater part of their weight, may be isomorphous, even when the elements in which they differ do not constitute by themselves an isomorphous group. M. Delafontaine read a memoir on the atomic weight of thorine or thorium. He has repeated the analysis of the sulphate of thorium after the method of Berzelius. The mean of several accordant results yielded him for the equivalent of thorine the figure 823.3, and admitting that the formula of this is Tho2, the weight of its atom referred to oxygen would be 1,646.6, and that of thorium 1,446.6. To the same author we owe a note on the place which thallium should occupy among the elements. Several chemists place it among the alkaline metals, while others consider it as being related to lead. Of these two views our colleague adopts the former.

Verbal reports.-M. Clusius has modified his theory on the atomic composition of ozone. It is not this body, it would seem, but oxygen which is formed of atoms grouped two and two-atoms which are dissociated when oxygen passes into the state of ozone. But it is objected to this new theory that ozone having more density than oxygen, it is the former, not oxygen, which must be composed of grouped atoms.

NATURAL SCIENCES.

GEOLOGY.-Memoirs.-M. Favre has continued his communications on the geological constitution of the Chablais. The soil of this province is composed of new formations superposed in the following order: the glacial, fucoid schists, kimmeridgian 1.mestone, collovian limestone, liasian, lower lias, triassic, coal, and serpentine. One of the characters of the region is the absence of cretaceous and nummulitic formations; an absence which results probably from the soil in question having been already elevated above the surface of the water at the epoch of the cretaceous and nummulitic seas. The author afterwards presents a geological description of that part of Savoy traversed by the valleys of Mégeve and of Haut-Luce. Among other formations he there recognizes the black slates of the jurassic period, forming the crest of Mont Joli; a fine deposit of vegetable fossils of the carboniferous era, near Bonhomme; and near Beaufort deposits of anthracite. He also shows that the granitic group of Mont Blanc is separated from that of Beaufort by sedimentary rocks, a continuation of those of the valley of Chamounix, and thus the granite of Beaufort would seem to be a prolongation of that of Valorsina.

M. Favre also gave an account of an investigation in which he is engaged of the deposits of translation between Jura and the Alps. These deposits present four principal stages: 1st, the present alluvium; 2d, the alluvium of the terraces, deposited by great currents of water above the glacial formation, and at a maximum elevation of 30 to 33 metres above the lake; 3d, the glacial deposit, composed of loam, of rolled pebbles, and of some erratic blocks; 4th, the old