HYDROLOGY. 85 
It was found that the results of the investigation of underground 
waters were of great interest to the public, and the rapid development 
of many areas in the West through the use of underground water for 
irrigation, the application of well waters to the irrigation of rice in 
the Southern States, and the ever-growing importance of deep well 
waters as sources of public water supplies have led in the last few 
years to a great increase in the work involved in their investigation. 
In order satisfactorily to meet the new demands and to develop, 
specialize, and systematize the work, the investigations relating to 
underground waters were segregated from the division of hydrography 
and grouped into a distinct organization known as the division of 
hydro-geology, or hydrology. This organization was made at the 
beginning of 1903, with two sections, western and eastern, the first 
including the so-called reclamation States and Territories and Texas, 
and the second embracing the States east of the Mississippi and those 
bordering that river on the west. Each of these sections was placed 
in charge of a geologist assigned from the division of geology and 
working under the general supervision of the chief hydrographer. 
In the western section there are three assistant geologists, two field 
assistants engaged throughout the year, and five field assistants engaged 
for a portion of each season. Special investigations are being con- 
ducted by several other geologists, in most cases State geologists and 
professors of geology at the State universities. In the eastern section 
there are several assistant geologists and many temporary field assist- 
ants. Arrangements have been made for cooperation by a number of 
local geologists, and several members of the geologic branch are giving 
special attention to restricted areas. 
The work of the division includes the gathering, filing, and publi- 
cation of statistical information relating to the occurrence of water in 
artesian and other deep wells; the gathering and publication of data 
pertaining to springs; the investigation of the geologic occurrence, 
from both stratigraphic and structural standpoints, of underground 
waters and springs; a study of the laws governing the variations due 
to tidal, temperature, and barometric fluctuations; direct measure- 
ments of rate of underflow; detailed surveys of regions in which water 
problems are of great importance and urgency, and the publication of 
reports on irrigation, city water supplies, and other important uses of 
underground waters. 
To serve as a basis in outlining plans for field work, it was found 
desirable to undertake a preliminary correspondence by means of 
printed requests for the addresses of drillers, well owners, spring 
owners, etc., and for information relating -to town water supplies, 
wells, and springs. Requests for addresses are first sent to post- 
masters, and to the addresses thus obtained special blanks are sent. 
The same system is used in gathering information from scattered 
