6 THE VOYAGE OF H.M.S. CHALLENGER. 



be seen by the analyses : in hardness it is inferior to felspar, and shows a greyish 

 or greenish-grey streak. The fracture is commonly even. The fragments are often 

 angular, and have sharp edges ; when of larger size they frequently show irregular 

 forms. 



The analysis which Professor Brazier made of a hard and compact specimen, very 

 slightly altered, and yielding by trituration a greenish powder, gave the following 

 result : — 



I. (B). 



Soluble in HC1. = 73-53 



Insoluble in HC1. = 2597- 



100-00 



We give here the result of another analysis by Dr. Sipocz : — 



The specific weight of the rock at 20*4° C. is 3*287. 



Firstly, l - 0586 gramme of substance, fused with carbonate of soda and potash, gave 

 0*0113 gramme of water (H 2 0). 



Secondly, 1*0853 gramme of substance, fused with carbonates of soda and potash, 

 gave 0-4758 gramme of silica (Si0 2 ), 0*1061 gramme of oxide of iron (Fe 2 3 ), 0*0124 

 gramme of alumina (A1 2 3 ), 0*0046 of oxide of chrome (Cr 2 3 ), 0*0014 gramme of 

 manganese peroxide (Mn 3 4 ), 0*0056 gramme of protoxide of nickel (NiO), 0*8186 

 gramme of lime (CaO), and 1*3353 gramme of PoOyMg,,, equal to 0*4801 of magnesia 

 (MgO). 



Thirdly, 0*7140 gramme of substance, treated with fluorhydric and sulphuric acid 

 for the determination of the ferrous oxide (FeO), required 10*7 c.c. of permanganate of 

 potash (1 c.c. of permanganate corresponding to 0*004547 gramme of iron (Fe), or to 

 0*085846 gramme of protoxide of iron (FeO), which corresponds to 0*1038 gramme of 

 protoxide of iron (FeO). 



Fourthly, 1*0024 gramme of substance was treated with concentrated chlorhydric 

 acid, the silica (Si0 2 ) being then removed by carbonate of soda (Na 2 C0 3 ), the residuum 

 obtained was 0*2830 gramme, equal to 28*30 per cent, of the peridotic rock left 

 unattacked. 



