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



described, have been subjected to chemical analysis. I will give a brief account of the 

 results, with a few succinct remarks drawn from the lithological examination of each. 

 The specimen whose composition is represented by the following analysis, No. 3, is made 

 up of peridotite, more or less altered to serpentine. The ground-mass is cut up by little 

 veins, or septa, of a blackish substance much harder than the surrounding body. Hence 

 the septa stand partly out in relief, and the phosphate has collected around them in con- 

 cretions. The fragment analysed must have been taken from a part of the rock showing 

 fewest signs of alteration. 



III. (B). 



Loss by heat at 230 Fahr., 

 Alumina, 

 Oxide of iron, 

 Phosphate of lime, 



_ nn Protoxide of iron, 

 Part soluble in HC1 = 85 '00 -{ , 



Sulphate of lime, 



Carbonate of lime, 

 Magnesia, 



. Silica, .... 

 Alumina, 



Part insoluble in HC1= 10-80 



Oxide of iron, 

 Magnesia, 

 L Silica, 



100-00 



The fourth analysis is that of a breccia formed in a fissure of the olivine rock. It 

 consists of fragments of olivine rock, 2 to 3 cm. long, and of the debris of highly altered 

 decomposed bones, whose organic structure is almost entirely obliterated. We notice in 

 these specimens fragments that look like rounded pebbles. The predominant feature of 

 these brecciform rocks is that of pseudo-fragments, i.e., fragments formed in situ in the 

 fissures of the rock, which, widening by decomposition, became filled with serpentinous 

 matter and phosphate of calcium. The phosphatic material readily disintegrates and 

 yields a whitish impalpable powder. It was the more or less impure phosphate that 

 gave the following analysis : 



IV. (B). 



Loss by heat at 230 Fahr., . . . . . . .4-40 



Oxide of iron, ....... 1-42 



Phosphate of lime, . . . . . . .82-65 



Protoxide of iron, ....... traces 



Oxide of manganese, . . . . . . . )} 



Sulphate of lime, ....... 4-76 



Carbonate of lime, . . . . . . . 4-86 



Carbonate of magnesia, . . . . . . 1-41 



Eesidue, ........ 0-50 



100-00 



