174 
GEOLOGY: W. BOWIE 
Bouguer range is from +0.017 to —0.110 dyne. The free air means 
vary from +0.058 to -0.008. 
It is important to consider whether the compensation occurs directly 
under a topographic feature, a mountain mass for instance, or is dis- 
tributed through a column having a cross section somewhat greater in 
area than the base of the feature. 
The compensation was distributed in horizontal extent to distances 
of 19, 59 and 167 kilometers in all directions from the stations. These 
distances correspond to the outer limits of zones K, M and O, which 
were used in computing the topographic and compensation corrections. 
It was found that the mean anomaly with and without regard to sign, 
was approximately the same for each method of distribution horizon- 
tally and for local distribution, if all stations were treated as a single 
group. Consequently, no one method seemed to be more probable 
than any other. The stations were next considered in five groups, 
according to the topography, with the results shown in the following 
table. 
Relation of Local-Compensation Anomalies and Regional-Compensation 
Anomalies to Topography 
ANOMALY 
ANOMALY. 
REGIONAL-COMPENSATION 
LOCAL 
COMPENSA- 
TION 
Zone K 
Zone M 
Zone 0 
19 km. 
59 km. 
167 km. 
At 18 Coast Stations 
Mean with regard to sign 
-0.004 
-0.004 
-0.004 
-0.006 
Mean without regard to sign 
0.018 
0.018 
0.018 
0.020 
At 25 stations near coast 
-0.002 
-0.001 
-0.001 
-0.001 
0.022 
0.021 
0.021 
0.022 
At 39 int erior stations, not in mountains 
Mean with regard to sign 
-fO.OOl 
+0.002 
+0.002 
+0.003 
Mean without regard to sign 
0.017 
0.018 
0.018 
0.017 
At 22 mountain stations below general level 
0.000 
+0.001 
+0.003 
+0.006 
0.017 
0.017 
0.018 
0.019 
At 18 mountain stations above general level 
+0.003 
+0.003 
0.000 
-0.010 
0.018 
0.018 
0.017 
0.020 
The mean anomaly without regard to sign is not decidedly in favor 
of either method. But the means with regard to sign seem to point 
strongly against the distribution of the compensation out to a distance 
of 167 kilometers from the stations, for there we have a range in the 
mean anomalies of 0.016 dyne between the 22 stations in mountainous 
