290 Explorations West of the 100th Meridian. 
The vapors that escaped from the steatite were caught by the 
slate above, and formed as vein matter in the fissures. 
Further development of this probably unique deposit may 
lead to a change in this theory, but at present it seems the 
only hypothesis to account for the presence of this pure borate 
in a substance which does not itself possess any trace of either 
the acid or lime. 
Art. XXXIII.—Ezxplorations West of the 100th Meridian. 
(Communicated by Dr. H. C. Yarrow.) 
Tue third field season of explorations and surveys under 
Lieut. Geo. M. Wheeler, Corps of Engineers, was brought to a 
close about the beginning of December last, and the scientific 
corps is now busily engaged in office-work in Washington, 
elaborating the data obtained. The areas embraced in the sea- 
son’s work covered western and southern Utah, eastern Nevada 
and northern Arizona, as far as the Grand Cafion of the Colorado, 
and taken in connection with the labors of 1869 and 1871, 
amount in extent to the territory of the New England an 
Middle States combined. These three surveys, in 1869, 70 and 
‘72, have been made to supplement and perfect each other in 
such a way that the Lieutenant’s mapped field now extends 
from central California over a large part of Nevada, as far east 
as central Utah, and south over the larger part of northern, 
western and central Arizona. ; 
The initial aim in the work of the Survey is the accurate 
mapping of the countries traversed, and the correction of the 
engineers’ map of the United States west of the 100th meridian. 
For this purpose there is a corps of trained topographers con- 
nected with the expedition, whose operations during the past 
season were much facilitated, and the accuracy of their results 
much enhanced, by means of a comprehensive series of astro- 
nomical stations, at various points, either nearly or remotely con- 
nected with the field of survey, extending from Cheyenne, 
Wyoming, on the line of the Union Pacific, to Beaver, in lower 
Utah. The value of these astronomical stations, and the tables 
the region surveyed, and the accumulation of data from this 
source alone is great. i 
mineralogy, meteorology, natural history, and capers. were 
filled and administered with vigor, sid“ valuable ga 
