CHEMICAL RESEARCHES. 51 
investigation. In the first place, it has been found that mam sub- 
stances supposed to be relatively rare are very common and widely 
diffused. The supposedly rare element, titanium, for example, is 
almost invariably found in appreciable quantities, and the average 
percentage of titanium dioxide in eruptive rocks is found to be nearly 
0.073. Barium and strontium are also commonly found in igneous 
rocks, especially in those of the Rocky Mountain region. Chromium 
and nickel are by no means unusual; even vanadium and zirconium 
are commonly encountered. By means of these analyses the petrog- 
raphers have been enabled to study rocks much more thoroughly on 
the chemical side than ever before, and it has been possible to com- 
pute with very close approach to accuracy the average composition of 
the earth's crust. 
In mineralogy much has been accomplished. Over 500 analyses of 
minerals are found in the records of the Survey, representing over 150 
species. Fifteen of the latter were discovered by the chemists of the 
Survey as new. In other cases little-known species and rare minerals 
were completely analyzed for the first time, and in still other cases 
the nature of species of doubtful composition has been thoroughly 
determined. The mineral analyses of the Survey have been brought 
together in Bulletin No. 220. 
Many analyses of natural waters from mineral springs and from 
mines have been made. The most important group of these, however, 
represents the waters of the Yellowstone National Park, and were 
published in Bulletin No. 17. These waters are unique in character, 
and of considerable variety. Most of the geyser waters contain 
appreciable quantities of such unusual substances as boric acid, arsenic, 
and lithia, and one water in particular — the water of the spring known 
as The Devils Inkpot — is unique, containing a little over 3 grams to 
the liter of solid salts, and 83 per cent of this saline matter is ammo- 
nium sulphate. From the water of this spring 2.8 grams per liter of 
ammonium sulphate can be extracted. Ordinarily ammonia in natural 
water is attributed to the decomposition of organic matter, but in this 
case it is of volcanic origin, and is probably brought from nitrogen 
compounds existing at great depths. In connection with the analyti- 
cal work of the laboratory, special attention has been given to improv- 
ing analytical methods, with the result that many new ones have been 
worked out. Notable among these are the determinations of titanium, 
lithium, and boron. The experience thus gained has been recorded in 
Bulletin No. 176, which is recognized as a standard work of reference 
by students and specialists, and is extensively used in university lab- 
oratories. It has been translated into German, and is recognized all 
over the world as the standard authority on silicate analysis. 
Technical chemists engaged in manufacturing or metallurgic estab- 
lishments are in the habit of using rapid methods of considerable 
