556 



SCIENCE 



[N. S. Vol. XL VI. No. 1197 



underlying the surface were replaced by com- 

 mon salt with, a specific gravity of 2.10 or 2.20, 

 the effect on the intensity of gravity might be 

 observable. If a still heavier mass made up 

 of salt, dolomite, igneous rock, etc., having a 

 specific gravity of 2.50 to 2.75 were intruded 

 the rate of swing of the pendulum would be 

 very perceptibly increased. If, however, only 

 a quarter of a cubic mile of the clay and sand 

 were replaced with the lighter or heavier sub- 

 stances, the effect would scarcely be observ- 

 able, and if the intrusion occurred several 

 thousand feet below the surface it might not 

 be possible to locate the position with the 

 gravity instrument. Other instruments have 

 been devised for measuring the intensity of 

 gravity that do not make use of the pendulum, 

 and it seems within the range of possibility 

 that in time an instrument of some sort will 

 be perfected by which more delicate observa- 

 tions can be made. 



The writer has found but one published 

 statement suggesting the use of gravity anom- 

 alies in the search for oil, and this was not in- 

 tended to apply in the way here outlined. 

 Eotvos,^ in 1913, suggests that it may be pos- 

 sible to find water, ore, coal, salt, oil and gas 

 by using gravity anomalies. David White* 

 has, however, studied the relationships be- 

 tween gravity anomalies and character of 

 rocks. 



On account of the slight variations in alti- 

 tude and latitude in southern Louisiana and 

 Texas and other regions where salt domes 

 occur, it seems possible that a considerable 

 part of the calculations made in connection 

 with the occupation of stations for other pur- 

 poses may be eliminated. The use of gravity 



3 EotvQs, Roland, TJngarn. Bericht uber Ar- 

 beiten mit der Drehwage ausgefiihrt im Auftrage 

 der Kon. XJngarisehen Eegiergung in den Jahren 

 1909-1911: Internat. Erdmessung, 17 AUg. Conf., 

 Hamburg, 1912, Beilage A, XL., pp. 427^38, 

 1913. 



4 White, David, ' ' Discussion of Gravity Anoma- 

 lies from the Stratigraphic Standpoint" (no ab- 

 stract). Discussed by William Bowie: Washing- 

 ton Acad. Sei. Jour., Vol. 7, No. 10, p. 312, May 

 19, 1917. Meeting of Geol. Soc. of Washington. on 

 March 14, 1917. 



observations in the search for salt domes 

 would then consist essentially in determining 

 at many points the number of beats in a unit 

 of time of a pendulum so constructed and en- 

 cased as to reduce the friction to the lowest 

 point possible. If the material in many of 

 the domes will perceptibly affect the number 

 of beats then it may be that gravity anomalies 

 can be used profitably in searching for hidden 

 domes, the observations for most points in a 

 county or group of counties being uniform, 

 while at a few points a perceptible departure 

 can be observed. The increasing value of oil 

 and the keen interest in prospecting make it 

 seem possibly worth while to make some prac- 

 tical tests with the gravity instrument on a 

 known salt dome and surrounding country, 

 especially since many wells are being sunk at 

 random in the region. To be sure, some salt 

 domes are known which do not seem to have 

 oil pools, and others are known which have not 

 yet been fully tested, but the number of insuffi- 

 ciently tested domes is rapidly decreasing, and 

 with the keener interest in the search for oil 

 the time will no doubt soon come when it will 

 be profitable to spend a great deal of money 

 searching for salt domes, for they seem to be 

 much more likely to contain oil than the sur- 

 rounding country. 



Eugene WesIjEY Shaw 

 TJ. S. Geological Survey 



ANNUAL FIELD TRIP OF THE AMERI- 

 CAN ASSOCIATION OF STATE 

 GEOLOGISTS 



The American Association of State Geolo- 

 gists made a very pleasant and instructive trip 

 through Oklahoma, October 12 to 16. At the 

 winter meeting in Albany, in December, 1916, 

 it was decided to hold the summer field meeting 

 in Oklahoma, and the Oklahoma Geological 

 Survey accordingly made very comprehensive 

 plans for the entertainment of the association. 



The declaration of war and the consequent 

 interest of the geologists in war materials 

 lead to the combination of the first part of the 

 field trip with the meeting of the American 

 Institute of Mining Engineers. 



After the meeting of the American Institute 

 of Mining Engineers ended at Drumright the 



