304 SOCIETY OF PHYSICS AND NATURAL HISTORY OF GENEVA. 



M. Soret coiiiinimicated tlie results of -recent observations on solar 

 radiation, the intensity of wliicli at Geneva during several days of IMarch 

 was very considerable and exceeded that wliich he liad observed in 

 summer at an altitude of 3,000 metres, (10,000 feet.) The same member 

 presented a memoir on the i^olarization of the blue light from water, 

 which has, under this condition, an almost complete analogy with the 

 light from the sky, {Archives, May, 1800.) 



§ 4. — Chemistry. 



M. Antoine Morin stated to us the result of his experiments on the 

 alloys of gold, silver, and copper, a subject which intimately concerns 

 our manufactures of jewehy and horology. The most usual alloys are 

 not only compounds but a true chemical combination, notwithstanding 

 the difference of density of the gold and copper. There needs but simple 

 fusion and remelting three or four times to obtain an alloy so homoge- 

 neous that the law allows only a deduction of j-^jj-^ for those of gold and 

 copper and of j-Jv o for those of silver and copper. For this there is 

 required a special force, which is chemical affinity, the influence of 

 which is demonstrated by a change in the molecular state of the metals 

 alloyed. In calculating the speciiic weight of alloys, we find a number 

 greater by an eighth or a ninth than the real density of alloys of gold, 

 and by a sixth or a seventh than the alloys of gold and native silver of 

 Colombia. The difference is insignificant for alloys of silver and copper, 

 but the homogeneity of the ingots is obtained with more difficulty. The 

 augmejitation of volume of the metals which enter into the alloys of 

 gold with silver and copper is not the only indication of a chemical com- 

 bination. The proportions which have been adopted in practice for 

 jewelry of 18 and 14 carats are closely approximate to the atomic num- 

 bers which would form combinations of a definite proportion. The 

 hypothesis that there is chemical union, and not simple mixture, seems 

 to be confirmed by the analysis of natural alloys. In most of these the 

 metals are found in quantities corresponding to the exact numbers of 

 equivalents. 



M. Morin has also been engaged in verifying the cause of the rochage 

 which forms an accident in founding, and which consists in a rupture 

 of the solidified crust of the metal accompanied by a jet of that which is 

 in fusion. He thinks thtit the rochage is a phenomenon of a chemical 

 nature, as the metal ejected has not the same comj)osition as the rest of 

 the ingot. 



§ 5. — Geology^ and Paxeontology^. 



Professor De La Eive communicated to us a letter of Professor Agas- 

 siz on the existence of ancient glaciers of considerable height and extent 

 in the greater i)art of North America, particularly in the region of the 

 prairies. 



Professor Favre described the great moraines which the ancient gla- 

 cier of the Ehiue has deposited even in Wlirtemberg. He gave an 

 account, based on the researches of two geologists of Lyons, (MM. Fal- 

 san and Chartre,) of the erratic blocks deposited by the glacier of the 

 Ehone between Geneva and Lyons, of the geological constitution of 

 Mount Cervin, as studied in two successive ascents by M. Giordano, of 

 the discoveries of M. Chartre relative to the question of prehistoric man, 

 &c. He exhibited to us a small erratic block of red porphyry, found in 

 the environs of St. Julieu, and, on several occasions, occupied our atten- 

 tion with the remarkable rei^ository of smoky rock-crystals, found at the 



