170 TRANSACTIONS OF THE SOCIETY OF PHYSICS AND 



is in progress. An engineer, M. Stapff, has been engaged to make a 

 careful section, indicating the strata, and to form 60 collections of the 

 rocks extracted, of which twenty-five will remain in Switzerland and 

 be distributed to the different museums of the country. M. Ernest Favre 

 has given us an account of the researches M. Stapff has already made 

 in the field of his commission. 



M. Alph. Favre has shown that upon the flank of the Jura, in the re- 

 gion of Gex, above Farges, erratic blocks are not found higher than 

 from 2,700 to 2,790 feet above the sea, while more to the east upon the 

 Jura and at the Saleve they are seen at a much greater elevation. He 

 thinks this may be accounted for by the small height of the Sion 

 Mountain over which the neighboring glacier could flow. The declivity 

 of Divonne, on the contrary, would interrupt its expansion in the direct 

 tion to the east of Gex. 



Chemistry. — Professor Marignac read a memoir upon the solubility of 

 the sulphate of lime, and upon the state of higher saturation of its 

 solutions, which was published in the Archives of Physical and Natural 

 Science for October, 1873. 



In another series of experiments, M. Marignac examined the diffusion 

 of two salts in the same liquid. He used salts not susceptible of recip- 

 rocal decomposition. In comparing salts capable of forming double 

 salts with those not thus capable, he found no difference. He perceived 

 no relation between the simultaneous diffusibility of two salts and their 

 relative co-eflicients of diffusion. The mingling of two salts diminishes 

 always the diflusibility of the least diffusible of the two. The various 

 acids and the various bases preserve their order of difl'usibility through- 

 out all their combinations. M. Marignac perceived no separation of the 

 acids ajid of the bases in the diffusion of the salts. 



A so-called kaolin was found at Colouges, near to the fort of the 

 ficluse. M. Emile Ador made an analysis of it. He found 38 percent, 

 of silica, 35 of aluminum, and 27 of water; consequently, it was not a 

 kaolin, but a mineral, analogous to the Halloyite. 



Zoology, physical, animal, and medical. — The presence of eels in the 

 Lake of Geneva has been sometimes denied, but also as often asserted. 

 M. Lunel was assured that this year several of them had been taken. 

 He attributed this fact to the elevation of the waters, which allowed the 

 eels to mount to the mouth of the Rhone more easily than iisual. 



The disappearance of a species is generally slow, and more or less 

 difiQcult to prove ; but, as an entirely exceptional instance, M. do Can- 

 dolle cited the complete absence since 1873 of the Galcricula calmari- 

 ensis, a small coleoptera, which for several years devoured the leaves of 

 the elms in the suburbs of Geneva to such a degree as to cause the 

 death of a large number of the trees. The i)roprietors in vain endeav- 

 ored to exterminate the insects, when suddenly they disappeared. As 

 this disappearance was general as well as sudden, it could not be attri- 

 buted to the increase of an enemy, but must have been due to an 

 irregularity at au important moment of some condition of its existence. 



