from the Atlantic, westward, to the zone which separates the mountain
region from the great valley of the Mississippi. Mr. G.K. Gilbert has
charge of this work, and has a large corps of assistants.

Sixth, it seemed desirable, partly for scientific reasons and partly for
administrative reasons, that a thorough topographic and geologic survey
should be made of the Yellowstone Park, and Mr. Arnold Hague is in charge
of the work, with a corps of assistants. When it is completed, his field
will be expanded so as to include a large part of the Rocky Mountain
region, but the extent of the field is not yet determined.

It will thus be seen that the general geologic work relating to those
areas where the terranes are composed of fossiliferous formations is very
imperfectly and incompletely organized. The reason for this is twofold:
First, the work cannot be performed very successfully until the maps are
made; second, the Geological Survey is necessarily diverting much of its
force to the construction of maps, and cannot with present appropriations
expand the geologic corps so as to extend systematic work in the field
over the entire country.


ECONOMIC GEOLOGY.

Under the organic law of the Geological Survey, investigations in economic
geology are restricted to those States and Territories in which there are
public lands; the extension of the work into the eastern portion of the
United States included only that part relating to general geology. Two
mining divisions are organized. One, in charge of Mr. George F. Becker,
with headquarters at San Francisco, California, is at the present time
engaged in the study of the quicksilver districts of California. The