268 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, No. 13 
to bring the subject before the geodesists of the countries adhering to 
the Union with a view to having it considered in detail at the meeting 
of the Geodetic Section which will be held at Madrid, Spain, in 1924. 
At that meeting it is hoped some definite plan may be adopted for 
applying the theory of isostasy to the treatment of gravity and 
deflection of the vertical stations. It is very desirable that uniformity 
in the treatment be agreed to by the several countries. 
The field work done in the United States by the Coast and Geodetic 
Survey during the year, which can be used in isostatic investigations, 
consists of astronomic observations for latitude, longitude, and 
azimuth at triangulation stations, and the establishment of gravity 
stations. 
The locations of eighteen of the gravity stations were selected by 
Dr. David White of the U. 8. Geological Survey with a view to testing 
the effect on the value of gravity of variations from normal density 
in the material near the stations. The computation and adjustment 
of the observations made have been completed, and the results fur- 
nished to Dr. White. He expects to make an analysis of the data in 
the immediate future. 
There are a number of localities in the United States where there are 
gravity stations close together which show great differences in the 
anomalies in very short distances. In the vicinity of Puget Sound 
the gravity anomaly at the Seattle station is —0.093 dyne, ‘while. 
at a point 15 miles to the westward the anomaly is only —0.025 dyne, 
and at a distance of 20 miles to the northwest of Seattle the anomaly 
is +0.002 dyne. At Tacoma, 27 miles south of Seattle, the anomaly is 
—0.012 dyne, and at Olympia, 50 miles to the southwest, the anomaly 
is +0.033 dyne. 
There is an anomaly of +0.059 dyne at Minneapolis, whileat Baldwin 
about 40 miles east of that place the anomaly is —0.050 dyne. At 
Damon Mound, in Texas, the difference in anomaly at two stations 
only seven miles apart, is 0.035 dyne. At Compton, California, the 
anomaly is —0.050 dyne while at two stations within 11 miles of Comp- 
ton the anomalies are much less. 
When it is considered that an anomaly of 0.001 dyne will be caused 
by the attraction of a dise of material of indefinite horizontal extent 
and 30 feet in thickness, we can realize that the differences in anomalies 
at some of the groups of stations in the United States represent the 
positive or negative attraction of large masses of material. It is 
certain that the cause of these differences in the anomalies must be in 
the upper part of the crust very close to the stations. If the causes 
