LETTER OE TRANSMITTAL. 
Department of the Interior, 
United States Geological Survey, 
Washington, D. C, July 13, 1900. 
Sir: I herewith submit, with a request for its publication as a bul- 
letin of the United States Geological Survey, a manuscript dealing 
in very considerable detail with the subject of silicate rock analysis, 
with special regard to the practice in the Survey laboratory. It repre- 
sents, in largely rewritten and much extended form, that portion of 
Bulletin 148 which dealt with the same subject. The present publica- 
tion seems fully justified by the demand on the part of mineral chemists 
for Bulletin 148, the supply of which available for sale has been ex- 
hausted. 
Very respectfully. 
W. F. IIlLLEBRAND, 
( 'In ////•'./. 
Hon. Charles D. Walcott, 
Directoi* United States Gt <>l(><itc<il Survey. 
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