GRAVITY PROSPECTING ON GULF COAST 21 
Magnolia Oil Company, confirmed by other torsion-balance work and 
by pendulum work of the Gulf Production Company before being 
drilled. The Vacuum-Magnolia is also credited with discovering 
Iowa, Roanoke, and Cameron Meadows in Louisiana. 
In this paper, dealing only with developments, no mention is 
made of the undeveloped prospects or those more or less definitely 
condemned. It is possible that several prospects will be proved, as 
the result of further drilling, particularly those that show structurally 
high wells. In this respect it is important to bear in mind that some 
deep-seated geophysical dome prospects may be represented as cor- 
demned whereas in reality they lack only deep enough tests. 
Certain minima undoubtedly represent inceptive or aborted salt 
domes which either stopped in early Eocene time or were not uplifted 
later sufficiently to affect horizons within easy reach of the drill and 
commercial production. Some of these will be drilled when economic 
conditions and deep-drilling technique have improved, giving some 
encouragement for commercial success. 
RECENT DEVELOPMENTS IN TECHNIQUE AND INSTRUMENTS 
In torsion-balance field work great economies have been effected 
in operation of the crews. Preference has been shown for the smaller 
instruments because of their easier portability. The introduction of 
tungsten torsion wires instead of the platinum-iridium wires formerly 
used, has done away with a great number of fail stations due to 
temperature effects. This is particularly true where only five points 
are used of a three-position automatic registration, and there is no 
check of the drift of the rest position of the instrument due to tempera- 
ture variations. Recent investigations have shown that a proper ad- 
justment of the torsion head of a balance is essential to obtain reliable 
readings. This factor was not given all the consideration due it in the 
past. 
Recently a new type of torsion balance was brought to this 
country by the American Askania Corporation. The beams, instead 
of being horizontal, or Z-shaped, are hung at an angle on a double 
suspension attached at the bottom of the torsion wires. This arrange- 
ment saves space and the manufacturers claim that 20 minutes is 
enough to obtain a rest position for this compact little instrument. 
One hour and 40 minutes is sufficient to complete a station, a great 
saving of time. This instrument is easily portable and easily adjusted. 
Experiments have been made in this climate to determine its sensi- 
tivity to temperature changes where variations are very pronounced. 
The best test of its behavior was at a known location where several 
reliable instruments checked each other within the allowable of one 
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