70 Scientific Notices-'Minerahgy. [Jan. 



magnesia, combined with a certain quantity of silicate of protox- 

 ide of iron. In fact the measurement of crystals of the artittcial 

 silicate of iron and that of peridot demonstrate a perfect 

 identity. 



M. Walmstedt's analysis of the olivine of Mount Somma fully 

 confirms these views. It gives 



Oxygen. 



Silica 40-08 20-16 



Magnesia 44-24 17-12 



Protoxide of iron 15-26 3*47 



Protoxide of manganese 0-48 

 Alumina 0-18 



100-24 



And since the quantity of oxygen in the magnesia is equal to 

 five times that of the protoxide of iron, and the oxygen of the 

 silica equal to that of the two bases together, it follows that 

 olivine consists of one atom of silicate of protoxide of iron, and 

 five atoms of silicate of magnesia. — (Annales des Sciences 

 Naturelles.) 



Mineralogy. 



4. Comparative Analysis of the Elastic Bitumen of England and 

 France. By M. Henry, the younger. 



The French bitumen was found in October, 1816, by M, Olli- 

 vier, in the coal mines of Montrelais, distant a few leagues from 

 Angers, at the depth of 35 fathoms, in a rock of ophiolite, mixed 

 with veins of quartz and carbonate of lime. 



Physical Characters of the two Bitumens. — 1. That found in 

 Derbyshire is in brown, or blackish masses, slightly translucent 

 on the edges, and appears greenish by transmitted light ; it is 

 more or less soft and elastic; burns very readily with a white 

 flame, and exhales a bituminous sineil. Its specific gravity 

 varies from 0-9053 to 1-233. 2. The French bitumen presents 

 nearly similar characters ; its colour is very deep blackish-brown ; 

 it is opaque, inodorous, moderately compact, compressible, very 

 tenacious, and particularly very elastic ; by transmitted light it 

 is rather black than greenish. It floats on water, and burns 

 with a clear bluish-white flame and a bituminous odour. 



The composition of the two bitumens, according to M. Henry's 

 analysis, is, per cent. 



English elastic bitumen. French elastic bitumen. 



Carbon 52-250 58-260 



Hydrogen 7-496 4-890 



Nitrogen 0-154 0-104 



Oxygen 40-100 36-746 



100-000 100-000 



