386 EXPLORATION GEOPHYSICS 



An exterior view of the Askania meter is shown in Figure 231. The spring system 

 and the electrical measuring device are contained inside a thick-walled, air-tight 

 housing. All of the levers are so connected that they can be operated from outside 

 the housing. The levers include : the arresting lever for the mass (left side of Figure 

 231), a drum for changing the measuring range (right side of Figure 231), a device for 

 supporting a standard weight, and an arrangement for moving the spring. The last 

 two devices are employed only occasionally and are not usually necessary for taking 

 measurements. Levels with 60 second graduations are mounted inside the case and 

 can be observed from above through a glass window. The leveling screws on the lower 

 part of the instrument can be adjusted from the top of the instrument so that it is 

 possible to view the inside graduated levels while making adjustments. Inside the main 

 housing there is a triple-walled soft metal casing which holds a thermostat. The ther- 

 mostat requires 20 to 25 watts for a temperature rise of 10°. The current source for 

 operating the gravity meter is a 12-volt storage battery. 



Fig. 232. — Gulf underwater gravimeter sealed with all control equip- 

 ment necessary to operate. (Courtesy of Gulf Research and Development 

 Company.) 



The Gulf Underwater Gravimeter 



The problem of geophysical exploration of the continental shelf brought 

 about the development of an underwater gravimeter. f It is an adaptation 

 of the standard Gulf gravimeter, described in the preceding section, and 

 is illustrated in Figures 232 and 233. Measurements may be made in 

 water to a depth of several hundred feet. The meter is lowered to the 

 bottom by means of a cable and hoist operated by the engine of the small 

 power-boat used in such work. The complete meter weighs 300 pounds in 

 air but only 25 to 30 pounds when submerged. About 350 pounds of lead 

 weights are often added to increase the stability of the apparatus. The 

 working parts of the instrument are encased in a pressure housing, made 

 of aluminum alloy, which will withstand a 700-foot head of water. 



t T. B. Pepper, "The Gulf Underwater Gravimeter," Geophysics, Vol. 7, No. 1, Jan. 1941, 

 pp. 34-44. 



