1894.] Geology and Paleontology. 263 
General Notes. 
GEOLOGY AND PALEONTOLOGY. 
Trans-Pecos Texas.—The studies of Mr. Streeruwitz in western 
Texas have developed some interesting facts from both a scientific aud 
economic standpoint. The rocks are mostly older and newer eruptives 
and various metamorphics; the sedimentary, as now known, reach 
from the Silurian to the Cretaceous period, and Cenozoic deposits are 
probable. The petrography of the Igneous rocks has been reported 
upon by Mr. A. Osann in the Ann. Rept. for 1892, Geological Survey of 
Texas. The results of his examinations show the great diversity of the 
character of the rocks prevailing in the different mountain ranges 
and the great difference in time and conditions of their origin. 
Mr. Streeruwitz finds that the disintegration of the rocks in Trans- 
Pecos Texas is mostly the result of the rapid changes of temperature 
and deflation, the same forces active in the desert of Sahara. The rains 
are also the cause of another source of disintegration causing that pe- 
culiar shape of granite blocks peculiar to the Sahara called “ Pilzfel- 
sen.” Chemical action manifests itself in the formation of rows of 
caves in the stratified granular rocks similar again to the African 
deserts. 
The prevalence of ozone in West Texas is explained by the author 
as the result of the friction of the drifting sand grains among them- 
selves and along the surface of the soil and the rocks, which creates 
sufficient electricity to ozonize the oxygen of the atmosphere. 
In regard to the ores, Mr. Streeruwitz reports that the most of the 
mountain ranges of Trans-Pecos Texas are ore-bearing. These ores 
are of excellent quality and exist in paying quantities, along with 
building stones and material for art and decorative work, not to men- 
tion agates, sardonyx, opals and other precious stones. The difficul- 
ties in the way of mining these products are pointed out and ways of 
surmounting them suggested by the writer. Under existing conditions 
the mountain land of this region is practically valueless, and for lack 
of irrigation the flats are becoming less fertile from year to year. 
(Fourth Ann. Rept., 1892, Geol. Surv. Texas, Austin, 1893.) 
Estimates of the Duration of the Glacial Epoch.—At a 
recent : fthe Geol gical Society of America, Mr. Warren Upham 
