NOTES ON GRAVITY DETERMINATIONS. 
69 
in the Yellowstone park, where topographic data were not 
adequate, and a rectangular district was substituted. In 
tabulating the results a column has been added to aid in 
the appreciation of their quantitative value. It shows in 
feet the thickness of sheets of rock (indefinitely broad) com¬ 
petent to produce the local deviations from normal gravity, 
or, coining a convenient term, it expresses the excess or de¬ 
fect of gravity in rock-feet. 
The local measurements will be discussed with reference 
to the geologic provinces in which the several stations fall. 
West of the interior plain arp the Rocky mountains of Colo¬ 
rado and Montana, the Colorado plateau province, the Wa¬ 
satch plateau, and the Desert ranges. East of it are the 
Appalachian mountains, the Piedmont plain, and the Atlan¬ 
tic coastal plain. 
Table III. 
Gravity at Stations West and East of the Interior Plain. 
1. 
Station. 
Altitude of sta- ^ 
tion. 
Altitude of mean ^ 
plain. 
Excess of grav¬ 
ity over 980.151 
dynes. 
Correction to re¬ 
duce to mean p 
plain. 
Excess of grav¬ 
ity after reduc- g, 
tion to mean * 
plain. 
Excess of grav¬ 
ity (column 6) 
expressed in * 
rock-feet. 
Feet. 
Feet. 
Dynes. 
Dynes. 
Dynes. 
Rock-feet. 
Pikes Peak. 
14,084 
8,640 
+.259 
—.181 
+.078 
+ 2,300 
Gunnison. 
7,677 
9,050 
+.026 
+.046 
+.072 
+ 2,200 
Grand Canyon..... 
7,830 
7,850 
+.049 
+.001 
+.050 
+ 1,500 
Lower Geyser Basin. 
7,218 
7,850 
+.039 
+.021 
+.060 
+ 1,800 
Norris Basin. 
7,465 
7,850 
+.063 
+.013 
+.076 
+ 2,300 
Grand Junction. 
4,586 
6,560 
—.019 
+.066 
+.047 
+ 1,400 
Green River. 
4,078 
5,340 
—.057 
+.042 
_.015 
— 400 
Pleasant Valley Junction. 
7,189 
7,500 
+.035 
+.010 
+.045 
+ 1,300 
Salt Lake Citv (al. 
4,336 
4,340 
—.020 
.000 
__.020 
_ 000 
Salt Lake Citv ( b ). 
4,336 
5,840 
—.020 
+.050 
+.030 
+ 900 
Deer Park. 
2,525 
2,080 
+.057 
—.015 
+.042 
+ 1,300 
Charlottesville.... 
544 
830 
—.001 
+.009 
+.008 
+ 200 
Princeton. 
210 
200 
+.005 
.000 
+!005 
+ 100 
Boston. 
72 
117 
+.028 
+.001 
+.029 
+ 900 
Washington... 
46 
220 
+.048 
+ 006 
+.054 
+ 1 600 
Philadelphia. 
52 
(?) 
+.039 
[+.006] 
+!o45 
+ 1*300 
