BELLE [SLE TORSION-BALANCE SURVEY 1339 
Most of the terrane was poor. Except for a few stations on the dry 
land of the island, the stations were on the sea marsh, which in general 
is covered with coarse, hummocky grass. The marsh is so soft that an 
t1-foot length of 2-inch pipe can be pushed into the marsh, level with 
the surface, by two men and pulled up by three men. Each foot of the 
instrument tripod was placed on the top of such an 11-foot length pushed 
down flush with the surface of the marsh. The instrument house was 
placed directly on the marsh. At times the foot of the instrument was 
under water. It was impracticable to clear off and level the station site; 
and on account of the grass hummocks and the soft character of the mud- 
dy ground between hummocks, the conclusion was reached that less 
error would be introduced by neglecting the terrane correction of the 
marsh stations than by taking levels and calculating the correction. 
The instruments and shelter houses were carried by hand. On ac- 
count of the difficulty of movement across the marsh and the many 
readings which had to be taken at each station, only one station per dav 
per instrument could be obtained in the marsh. 
A long east-west line of stations on the beach, and eight radial lines 
of stations were occupied. An average station interval of 400 feet was 
used. Although stations in South Pond would have been desirable, no 
attempt was made to occupy them because of the difficulties in occupying 
stations in the water. 
Results of survey.—The results of the field survey are shown in Figure 
2. The results of the preliminary line of stations which were occupied 
along the beach showed that the dome extends south of South Pond but 
does not reach the beach, that probably considerable cap rock might be 
expected on the south end of the dome, and that it would be advanta- 
geous for the Freeport Sulphur Company to make a detailed torsion- 
balance survey of the dome. 
The results of the west, southwest, south, and southeast radial lines 
of stations showed that the Belle Isle salt dome is elliptical in plan, that 
its major axis has a north-northeast strike and a length of approxi- 
mately 2 miles, and that much cap rock might be expected in a broad 
area south, southwest, and west of South Pond, probably at moderate 
depth. The approximate position of the edge of the dome.is delineated 
in the gradient arrow map (Fig. 2) by the zone of maximum gradient 
which from tangency to the east side of the island swings clockwise 
across the outlet to South Pond, then southwest and west of South Pond 
to tangency to the northwest edge of the island. 
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