SOCIETY OF PHYSICS AND NATURAL HISTORY OF GENEVA. 367 



velocity communicated to tliom l)y tlie strata into wliicli tlicy penetrate, and 

 wherein tbey difiuse themselves. 



§ 2. — METEOr.OLOGT. 



Professor A. Gautier read (4th July) an extended notice of the results obtained 

 from December, 1865, to November, 18GG, during the third year of observations 

 made at the 76 stations of Switzerland, under the two-fold view of temperatures 

 and quantities of rain. This production has been inserted in volume xxix of 

 the Archives dcs Sciences, Physiques, et KafurcJles. I will content mysell, there- 

 fore, with citing a conclusion hut little known ; namely, that the mean tempera- 

 ture of Geneva is higher than that of the other cities of our country, with the 

 exception of Bellinzona, Lugano, Mendrisio, Montreux, and Sion. At the close 

 of the last-mentioned communication. Professor A. de Candolle expressed a regi'et 

 that the methods by means of whicli meteorologists establish the mean of the 

 numbers they collect, render the results of their calculations nearly useless to 

 botanists. He remarked that the phenomena of vegetation continue for some 

 months, during which it would be important to know the sums of the tempera- 

 tures above a certain degree previously fixed upon. 



§ 3. — MATHEMATICS AND PHYSICS. 



The sun, that source of complex radiations which call forth the most diverse 

 and important phenomena, dispenses to us heat varying as to quantity with the 

 seasons, and as to composition with the state of the atmosphere. By means of 

 the actinometer which he ])resented last year to the society, INI. L. Soret com- 

 pared (5th September) the intensity of the caloriiic radiation at Geneva with its 

 value on the glacier of the Bossons and at the summi-t of Mont Blanc; he found 

 that when the sun is 60° above the horizon, the radiation at a height of 4810 

 meters is to that on tlie plain in the ratio of six to five. The dimiuutiou of 

 intensity with the height of the sun is much less considerable at a gi'eat altitude 

 than in regions less elevated. T^o these observations, made in August, il. Soret 

 lias added others during the winter, whence it results that, for the same height 

 of tlie sun, tlie intensity of the direct radiation is then greater than in summer, 

 Avliich accords with the part which, according to j\I. Tyndall, is borne by tiie 

 atmosplieric vapor in the phenomena of absorption. Our colleague has ascer- 

 tained that, at an equal elevation of the sun, the radiation diminishes more rap- 

 idly when the heat has traversed a watery stratum than when the rays are direct. 

 The recital of these results was the occasion of interesting discussions, calculated 

 to guide the author in new experiments. 



The question whether the sea is free at the pole was raised in connection with 

 these estimates of the thermic intensity of the solar radiation. M. Soret also 

 took occasion to state (I9th December) that ozone, prepared l»ythe action of the 

 apparatus of Ruhmkorff on f)xygen, jiossesses the same density with that obtained 

 by electrolyzing water. (Archircs dcs Sciences, (Cr., t. xxx, p. 306 ) 



Professiir de la Hi ve presented (6th February) the analysis of researches by 

 M. Elias Loomis, leading to conclusions very favorable to the electrii; theory of 

 ])olar auroras, proposed l)y our colleague. [Archives des Sciences, ^c.,t.xKx\, 

 p. 27.3.) 



Among the phenomena whose study promises to enlarge the field of our 

 knowledge of the intimate constituti(m of bodies, none are more interesting than 

 those of rotary polarization. Detected in quartz b}- Arago, in 1811, this mys- 

 terious property has l)een found in solids of regular system, in homogeneous 

 colorless licpiids, and in certain vapors, though no permanent gas, even when 

 compressed, has heretofore manifested it. It is therefore independent of tho 

 crystalline state, and, according to tho substance employed, takes placx) some- 



