88 THE UNITED STATES GEOLOGICAL SURVEY. [bull. 227. 
New York; measurement of velocity of underflow of water in sands 
and gravels; springs of New York State; underground water supplies 
of New Jersey; pollution of underground waters of Georgia; under- 
ground water resources of Louisiana and Arkansas; springs of Mis- 
souri; and artesian waters of Minnesota and Wisconsin. 
In part the field work has consisted of the running of levels connect- 
ing wells with railroad levels, thereby establishing a basis for deter- 
mining the structure of water-bearing formations. Such work has 
been conducted with success in southern Arkansas and Louisiana, 
where it is expected that it will aid in determining the most available 
water horizons for the supply of towns and cities, and perhaps lead to 
more extended use of underground water for the irrigation of rice. 
In Missouri promising results include the discovery of new artesian 
areas and the relations of temperatures of cavern and surface springs 
at similar horizons, the development of caves and sinks by underground 
drainage, and surface modifications resulting therefrom; and, in gen- 
eral, the origin, flow, and temperature of all underground waters and 
their economic uses. 
In the western section, among the more important results so far 
obtained are the amounts of variation in water levels at localities where 
water is being extensively utilized for irrigation, as in Salt River 
Valley in Arizona and San Joaquin Valley in California. In these 
and similar areas tests to determine the movements of underground 
waters have been made, and much light has already been thrown 
upon these obscure phenomena. 
In the Dakotas much attention has been given to special geologic 
work, with a view to ascertaining the relations of underground waters 
to the geologic structure. Reports and maps have been prepared 
giving a review of the artesian conditions in the great central plains. 
Figs. 4 and 5 show the progress of the hydrologic work. 
For publications on hydrologic subjects see the Survey's list of 
publications. 
DIVISION OF HYDRO-ECONOMICS. 
The entire hydrographic work of the Survey is, to a more or less 
extent, of an economic character. The special work of the division 
of hydro-economics may, however, be said to have been started with 
the gaging of rivers in the eastern portion of the United States, as the 
reason for this development was the need of data for water-power and 
other economic purposes. The first investigation of this nature was 
a study of the Potomac drainage basin, begun in April, 1891. 
Another development took place in 1895 with a general reconnais- 
sance and establishment of gaging stations in the southern Atlantic 
drainage basins in the States of Virginia, West Virginia, North Caro- 
