396 Scientific Intelligence — Geology. 



greater the alteration they have undergone. In diorites which have 

 undergone no alteration, M. Durocher has found the proportions of 

 water to vary from 0'008 to 0*020. The majority of trap rocks 

 contain from 0*020 to 0*060. In the pyroxenic porphyries, basalts, 

 and trachytes, there is usually, with rare exceptions, from 0*007 to 

 0*030, and in the pumices there is much more, from 0*030 to 

 0-070. In six volcanic lavas he found from 0*0045 to 0'0451 of 

 water. 



M. Durocher has ascertained the existence of carbonate of lime 

 and dolomite in many pyrogenous rocks when it is impossible to per- 

 ceive them by means of a magnifying glass ; he has discovered this 

 by treating small portions of these substances with acetic acid. He 

 has likewise found quantities of dolomite, varying from 2 to 13 

 thousandth parts in a granite from Stockholm, in a protogene of 

 the valley of Agly (Eastern Pyrenees), a petrosilex of Sala (Sweden), 

 a euphodite from Savoy, a basalt of St Flour, and in a vesicular and 

 peridotiferous lava from Auvergne. He has detected traces of car- 

 bonate of magnesia in a hyperstenic syenite from Norway. He 

 has also ascertained the presence of from 0*001 to 0*016 of car- 

 bonate of lime, either pure or slightly magnesiferous, invisible with 

 a glass, in 25 specimens of granitic, amphibolic, trap, basaltic, py- 

 roxenic, and trachytic rocks, as well as in lavas from different coun- 

 tries. 



Thus, independently of the silicates, the pyrogenous rocks con- 

 tain a little water and very often small quantities of earthy carbo- 

 nates, which appear to have formed part of them from the first, and 

 not to have resulted from infiltration. Frequently also they contain, 

 as is already known, small quantities of phosphates, fluorides, sul- 

 phurets, and arseneosulphurets. 



The magnetic property is much more common in these rocks than 

 is generally supposed. The granites alone are rarely magnetic. 

 The magnetism of these rocks appears to the author to be owing to 

 the presence of a small quantity of oxidulated iron, sometimes in tita- 

 niferous iron or magnetic pyrites. In other respects it is remarkable 

 that the greater part of crystalline rocks, even those which are not 

 magnetic, yield a little oxide of iron to boiling acetic acid ; when 

 they are calcined, they almost always assume a reddish or rose tint. 



M. Durocher concludes by adding that the Oligoclase, that species 

 of felspar which was first observed in the granitic rocks of the north 

 of Europe, is likewise found, though in smaller quantity, in those of 

 France. He has discovered it in a syenite of the Vosges, and in 

 numerous granites of the Alps, Pyrenees, and the west of France. — 

 VInstitut, No. 709, p. 249. 



2. Baron Voti JBuch on Glaciers. — I think I may now well ven- 

 ture on this conclusion, deduced from nature and experience, without 

 needing to fear uncalled for verbose, and therefore unmeaning, op- 

 position, since the singular doctrines of Venetz and Oharpentier, re- 



