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). 



Loss by heat, . . . . 0-50 



Oxide of iron, .... traces 



Protoxide of iron, . . . . 9 '5 6 



Sulphate of lime, . . . . 0-29 



Magnesia, ..... 31 '43 

 Silica, . . . . .32-25 



C Alumina, ..... 0'90 



Oxide of iron, . . . . 3 '40 



Lime, . . . . . 1'51 



Magnesia, . . . . . 5 '2 6 



L Silica, ..... 14-90 



Soluble in HC1. = 73 -53 



Insoluble in HC1. = 25 -97 



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, 1/0586 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 T3353 gramme of P 2 7 Mg 2 , equal to 0'4801 of magnesia 

 (MgO). 



Thirdly, 07140 gramme of substance, treated with fluorhydric and sulphuric acid 

 for the determination of the ferrous oxide (FeO), required 107 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, T0024 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. 



