GENEVA SOCIETY OF PHYSICS AND NATURAL HISTORY. 209 



protocatechic acid. With pure oxysalicylic acid, M. Demole obtained 

 bydroquiniDe aud a small quantity of pyrocatecbiue. The formation of 

 these two dioxybenzols is a curious fact, the theoretical explanation of 

 which is still rather obscure. 



The same member communicated a memoir, published January, 1875, 

 in No. 205 of the Archives, on the reaction of the bromide of ethylene 

 on diluted alcohol, in presence of the acetic ethers of glycol. M. Demole 

 made numerous experiments for the purpose of explaining the formation 

 of the products due to this reaction, namely, of glycol, bromhydrine, 

 acetate of ethyl, aud bromide of ethylene. 



2. I^atural sciences. — Prof. A. Favre submitted a communication on 

 the altitude of the glaciers at the Glacial era, and the height that must 

 be attributed to the summits of the Alps, if the slope of the glaciers 

 were the same at that time as at the present day. Among the maps 

 of the topographical atlas of Switzerland, executed by the Federal 

 Bureau of the Staif Office, there are some referring to the Bernese 

 Jura, in which are found represented, on the flanks of the Chasseral, 

 erratic blocks of considerable bulk, at altitudes varying from 1,200 to 

 1,300 metres (about 4,000 feet). These blocks have drifted from the 

 mountains which command the present glaciers of the Ehone, and are 

 260 kilometres (162 miles) distant from the Chasseral. By assuming that 

 the glaciers of the glacial era had a slope equal to the minimum slope of 

 the present glaciers, namely, from 2 per cent, to 1^ per cent., the result 

 would be a difference of altitude of 5,200 and 3,900 metres, (17,000 and 

 13,000 feet) respectively, between the upper and lower part. From the 

 altitude of the latter, which is 1,300 metres (4,000 feet), there would re- 

 sult 6,500 or 5,200 metres (20,000 or 17,000 feet), for that of the upper 

 part, or a sum greatly exceeding the height of the Galenstock, one of 

 the most elevated summits bordering on the glaciers of the Ehone, which 

 rises to a height of 3,600 metres, (12,000 feet). We would thus have 

 to adujit that either the height of the Alps at the Glacial era greatly 

 exceeded the ])resent height, or that the slope of the glaciers was con- 

 siderably less. This last hypothesis is quite admissible from the results 

 of the recent explorations of the polar regions, especially those of Green- 

 land, but nothing forbids the admission of the combined action of both 

 causes. 



Professor Favre also presented a memoir on the recession of the gla- 

 cier of the Bossous of late years, aud on the relation between the ad- 

 vance and retreat of glaciers and the atmospheric conditions, especially 

 the summer temperature. lu the last eight years, included between 

 July, 180G, and June, 1874, the glaciersof the Bossons receded 212 metres^ 

 ((il)6 feet), and at the latter date it was 682 metres (2,240 feet) in rear of the 

 point it had reached in 1818, the epoch of its greatest development in this 

 century. If within late years the retreat of the glaciers can be explained 

 by the elevation of the mean temperature, especially in the summer 

 months, their development at an anterior period can likewise be attributed 

 14 s 



