SOME PRINCIPLES AND METHODS OF ROCK ANALYSIS. 
By W. F. HlLLEBRAND. 
PART I.— INTRODUCTION. 
I. IMPORTANCE OF COMPLETE AND THOROUGH ANALYSES. 
The composition of the ultimate ingredients of the earth's crust — the 
different mineral species which are there found and of many of which 
its rocks are made up — was the favorite theme of the great workers in 
chemistry of the earlier half of this century, and for the painstaking 
care and accuracy of Berzelius, Wohler, and others the mineralogists 
and geologists of to-day have need to be thankful. Considering the 
limited facilities at their disposal in the way of laboratory equipment 
and quality of reagents, the general excellence of their work is little 
short of marvelous. As an outgrowth of and closely associated with 
the analysis of minerals came that of the more or less complex mix- 
tures of them — the rocks — to aid whose study by the petrographer and 
geologist a host of chemists have for many decades annually turned 
out hundreds of analyses of all grades of quality and completeness. 
With the growth and extraordinary development of the so-called 
organic chemistry inorganic chemistry gradually fell into a sort of 
disfavor. In many, even the best, European laboratories, the course 
in mineral analysis, while maintained as a part of the curriculum of 
study, became but a subordinate prelude to the ever-expanding study 
of the carbon compounds, whose rapid multiplication, offering an easy 
and convenient field for original research and possible profit, proved 
a more tempting opening to young chemists than the often-worked- 
over and apparently exhausted inorganic pasture. For one student 
devoting his time to higher research on inorganic lines were perhaps 
fifty engaged in erecting the present enormous structure of carbon 
chemistry. The instruction afforded the student in mineral analysis 
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