resetting in the factory. The Worden meters were purchased by the 

 Hydrographic Office in 1950. 



Recent improvements in the Worden gravimeter have upgraded the 

 quantity and quality of observations obtainable. The new Master model 

 includes low-power temperature stabilization, positive linear drift, 

 a gearless top-reading dial, and a world-wide range. The present 

 price of the new meter is about $8,500. 



b. North American gravimeter 



This meter is temperature controlled, thus eliminating drift, 

 and has a total range of 1,000 milligals. However, it can be used 

 world-wide by resetting it. The measuring element can be clamped 

 when not in use. Calibration by the manufacturer gives a constant 

 value over full range which appears to be good from field checks 

 made by this Office. 



The principle drawbacks of this meter are its size and weight and 

 the extreme sensitivity of the reading mechanism. Two people are 

 required to transport the meter in the field; it is time-consuming to 

 operate and requires frequent battery changes to maintain constant 

 temperature. This meter has not proven satisfactory for general use 

 by this Office, but it was the only instrument of its type available when 

 it was purchased in 1952. The price of this meter is about $8,500. 



c. LaCoste and Romberg gravimeter 



Two meters of this manufacture have been purchased by 

 the Hydrographic Office. The first meter, an early model, was pur- 

 chased in 1957 for $10,000. It is a temperature-controlled instrument 

 with a world-wide range usable without resetting. The calibration 

 by the manufacturer was made on a range at Cloudcroft, New Mexico 

 and is a straight line over the entire reading range. The meter is 

 easily read by means of a counter dial and has the most stable reading 

 indicator of all meters on hand. Very little drift occurs, and reading 

 continuity is not lost with loss of heat. The chief disadvantages of this 

 meter are its size and weight and the size and weight of the power 

 supply required for temperature control. These limit the utility of 

 this meter in that it is difficult to handle in the field unless the terrain 

 permits the use of a vehicle. 



The second meter was purchased in I960 for $10,000. This meter 

 is a miniaturized version of the previously described meter, and it 



XIII- 5 



