462 COSMOS. 



crystals of uralite, of from half a line to five lines in length, 

 with a perfect augite form and the cleavage of hornblende 

 (see Rose, Reise nacJi dem Ural, Bd. ii, s. 353)." I brought 



Alick's Analysis. 



(Height 16,179 English feet; spec. grav. 2.685.) 



Oxygen. 



Silicic acid 65.09 ... 33.81 . 2.63 



Alumina 15.58 ... 7.27 



Oxide of iron 3.83 ... 1.16 



Protoxide 1.73 ... 0.39 



Lime 2.61 ... 0.73 



Magnesia 4.10 ... 1.58 



Soda 4.46 ... 1.14 



Potash 1.99 ... 0.33 



Chlorine, and loss by ) ... 

 heat J 



99.80 



In explanation of these figures it must be observed, that the first 

 series gives the ingredients in a per eentage, the second and third give 

 the oxygen contained in them. The second space shows only the 

 oxygen of the stronger oxides (those which contain 1 atom of oxygen). 

 In the third space this is recapitulated, so as to offer a comparison 

 with that of the alumina earth (which is a weak oxide) and of the 

 silicic acid. The fourth space gives the proportion of the oxygen of 

 the silicic acid to the oxygen of the aggregate bases, which latter 

 are fixed = 1. In the trachyte of Chimborazo thia proportion 

 is -2.33:1. 



" The differences between the analyses of Rarnmelsberg and of 

 Abich are certainly important. Both analysed minerals from Chim- 

 borazo, from the relative heights of 19,194 and 16,179 feet, which 

 wei'e broken off by you and were taken from your geological collection 

 in the Royal Mineral Cabinet at Berlin. The mineral from the lower 

 elevation (scarcely 400 feet higher than the summit of Mont Blanc) 

 which Abich has analysed, posseses a smaller specific gravity, and in 

 correspondence therewith a greater quantity of silicic acid, than the 

 mineral taken from a point 2918 feet higher, analysed by Ram- 

 nielsberg. Assuming that the argillaceous earth belongs only to the 

 felspathic ingredient, we may reckon in the analysis of Rammels- 

 berg : 



Oligoclase 58.66 



Augite 34.14 



Silicic acid 4.08 



As thus, by the assumption of oligoclase, a portion of silicic acid 

 remains over uncombined, it is probable that the felspathic ingredient 

 is oligoclase and not labradorite. The latter does not occur witb 



