230 GENEVA SOCIETY OF PHYSICS AND NATURAL HISTORY. 



May to December, at G™. C (22 feet) ; in winter at 10"^. 1 (33 feet ;) iu March, 

 1875, it was necessary to sink it to 17°* (56 feet.) The limit of photo- 

 graphic action was found to be 45"! (148 feet) in summer, and 100™ (328 

 feet) in winter. According to the author the transparency of the water 

 of the lalje depends, first, upon the temperature; second, upon the pro- 

 portion of organic matter in suspension in the water. The latter is more 

 abundant in summer than in winter, because the waters of the lake in 

 the first of these two seasons present strata of different temperatures, 

 producing differences in density, and the result is that the organic 

 matter, also differing in density, will seek a stratum of a corresponding 

 density and will be there held iu suspension. In winter the temperature 

 of the water being more uniform, the substances are retained in much 

 less quantity. {Bulletin Soc. vaudoisc des Sc. nat, 1874, t. xiii; 1875, t. 

 xiv; and Comptes rendus de VAcademie des Sciences, 1877, t. 84, p. 311.) 



M. Eaoul Pictet has presented, iu regard to the intermittent fountain 

 of Vichy, a theory by which he has been enabled to explain the singular 

 movements of waters more clearly, since he has succeeded in construct- 

 ing an apparatus which produced them in miniature. This fouutain pro- 

 ceeds from a tube which descends to a depth of 107™ (351 feet), at the base 

 of which, therefore, there must be a pressure of ten atmospheres. The 

 eruption of water mingled with gas is produced for about an hour, rises 

 to ten or twelve meters (33 or 39 feet), and ceases for five or six hours. 

 If the pipe reaches a little below the most elevated portion of an im- 

 permeable vault which covers a part of the sheet of water, the gases 

 which are generated by the waters of Vichy accumulate in the vault, 

 drive the water to the lower edge of the conduit and escape with it 

 over the latter. (See Archives, 1876, t. 57.) 



M. Theodore Turrettini has made known the results obtained by M. 

 Pictet and himself in the fabrication of transparent ice by means of 

 the machine employed by the firm of Kaoul Pictet and Company. 

 As slow freezing of the water could not be managed, MM. Turrettini 

 and Pictet tried agitating the water under the pneumatic pump in 

 order to drive out the air, but the middle of the block of ice formed 

 was more or less opaque on account of a sort of crystallization. M. Tur- 

 rettini has at last succeeded in obtaining some perfectly transparent ice 

 by causing globules of air to pass through the water to be frozen, in a 

 continuous current. These large globules of air seemed to carry away 

 with them the small air-bubbles, which even more than the crystalliza- 

 tion appeared to cause the non-transparency of the ice. 



3. Geology and chonchology. — Professor Kenevier has exhibited a chart 

 of the Swiss Alpine Club on a scale of sqojto? colored geologically, pre- 

 pared for the federal commission of the geological chart of Switzerland. 

 It includes the most elevated parts of the Vaudois Alps, the rocks of 

 Diablerets, of the Muverau, &c., and extends along the right shore of the 

 Ehone to the north of Martigny in Valais, from the village of Ardon to 

 that of Ollen, to the north of Bex. This when published will be accom- 



