50 THE UNITED STATES GEOLOGICAL SURVEY. [bill. 227. 
plies from deposits in the United States by a general investigation of 
the occurrence of the mineral concerned. In this wa} r much help has 
been given to producers and others of such minerals as monazite, 
zircon, iridosmine, platinum, and lately minerals containing radium. 
The unusual interest aroused by the discovery of radium in certain 
minerals in the United States and elsewhere has caused a great demand 
for information concerning the minerals which show radio-active and 
radio- responsive properties. Therefore a special exhibit of minerals 
possessing these properties and of radium compounds will be shown 
as part of the exhibit of the Geological Survey at the Louisiana Pur- 
chase Exposition, to be held at St. Louis this year. 
For publications giving the results of the work of this division, see 
the Survey's list of publications. 
DIVISION OF CHEMICAL AND PHYSICAL RESEARCHES. 
Section of Chemistry. 
In 1880 a small laboratory was organized at Denver, Colo., on the 
recommendation of the geologist in charge of that division. In 1882 
another laboratory was organized at San Francisco, Cal., on the 
recommendation of the geologist in charge of geologic work on the 
Pacific coast. In 1883 a central laboratory was established in Wash- 
ington, and to this, by degrees, the equipment and personnel of the 
other laboratories were transferred. The consolidation was completed 
in 1890. 
In 1892 eight chemists were employed in this laboratory, but in that 
year the appropriations were so greatly decreased by Congress that 
the working force was reduced to three. Since then there has been 
gradual enlargement of resources, and at present six chemists are 
engaged on the chemical work of the Survey. 
Up to January 1, 1904, nearly 5,300 anatyses had been made in the 
Washington laboratory alone. These cover the entire range of prod- 
ucts in which the geologist is interested. Rocks of every description, 
ores, minerals, clays, coals, and waters have all received attention. 
A specialty of the laboratory has been the complete analysis of erup- 
tive rocks, and of these something like 1,000 have been made. Com- 
pleteness and accuracy have been the aim of the chemist engaged on 
this work, and it is believed that the thoroughness of the anal} T ses of 
rocks now carried out in the laboratory exceeds that ever before 
attempted. In Bulletin No. 168 the rock analyses were summed up 
to January 1, 1900, and a new edition of that bulletin is now in prep- 
aration. In the analyses of igneous rocks it is customary in the II 
Survey's laboratory to look for about 20 different constituents; com- 
monly, in analyses made elsewhere, from 12 to 15 are determined in a 
single rock. Two results have followed from this exhaustive plan of 
