CHAP, v.] GENKliAL CONCLUSIONS. 325 



No. 20.— Station XXIII. March 15tli. Off Sombrero Island. Depth, 

 450 fathoms. Chemical composition : 



Loss on iguition after drying at 230° F 4-00 



' Alumina 1 'StJ 



Ferric oxide 300 



Portion soluble in Calcium phosphate Good traces 



hydrochloric acid ^ Calcium sulphate 1 '00 



= 93-95. Calcium carbonate 84-2'7 



Magnesium carbonate 1"28 



Silica 2-60 



Portion insoluble 1 ^ , , , . , . . „ . . , i- ■ • i 



. , , , , . Insoluble residue, prmcipally alumina and lerric oxide, 



in hydrochloric \ . i i .? 



acid = 2-05. J 



with silica 2-05 



100-00 



A pteropod ooze, containing very many shells of pteropods and het- 

 eropods, and their broken fragments ; many pelagic foraminifera of the 

 genera Globigerina, Pidvlnulina, OrbuUna, Pullenia, and S^jhceroidi- 

 na ; large BilocuUnce and calcareons Rotalice and Cristellariw ; a few 



coccoliths. Amorphous clayey and calcareous matter, with sandy 



particles, quartz, feldspar, mica, magnetite, and sanidine. 



Notes on the Foregoing Analyses by Professor Brazier. 



The loss on ignition consists, for the most part, of water, probably 

 water of hydration ; but there is in all cases evidence of the existence 

 of organic matter. The majority of the specimens, when treated with 

 hydrochloric acid, evolved the peculiar tarry odor so characteristic of 

 some of the limestones of this country. This odor was most percepti- 

 ble in the specimens numbered 8, 9, 13, 19, 20. 



In all the specimens in which the quantity of material was sufficient, 

 the alkaline vapors which accompanied the moisture evolved were read- 

 ily recognized. 



The portion of the sample taken for analysis, after being treated with 

 hydrochloric acid, yielded in every case a residue of a whitish-gray color, 

 Nos. 10, 11, and 12 being nearly white. 



No. 8. — Material at command, 9 "80 grains. 



Loss on ignition 0-895 



Soluble in acid 7-506 



Insoluble in acid 1399 



9-800 



