96 REPORTS ON INVESTIGATIONS AND PROJECTS. 



the temperatures were measured with a precision of about 0.02°, the uncer- 

 tainty in the pressure measurements was about 5 atmospheres. In order to 

 insure accuracy in the measurements of pressure, an absolute gage has been 

 constructed. With this instrument, the principle of which is that the press- 

 ure acting upwards on a known area is balanced directly by the use of a 

 series of weights, pressures up to 1,000 atmospheres can be measured with 

 an absolute accuracy of i part in 1,000, while its sensibility, even at that 

 pressure, is such that differences considerably less than i atmosphere can 

 be detected. This gage and another on the same principle designed for 

 weighing still higher pressures are to be used to calibrate secondary gages, 

 which then, in the actual investigations, will be convenient and accurate to 

 use. 



In the work alluded to above we were limited to temperatures about 400° 

 and to pressures about 2,000 atmospheres. These limits have now been ex- 

 tended — separately at least — by the construction of a bomb capable of with- 

 standing 2,000 atmospheres, but so constructed that a temperature of 1000° 

 or more can be reached and maintained for as long a time as may be desired ; 

 while on the pressure side a multiplying arrangement has been completed 

 Avhich will enable us to develop and control pressures up to 5,000 atmos- 

 pheres (75,000 pounds per square inch). Incidentally to this work, types of 

 valves and pressure connections have been developed which can, as often as 

 necessary, be taken apart and put together again, and yet show no signs of 

 leak even at the highest pressures. Though but a technical detail, this device 

 is of vital import to the ultimate success of the investigation. 



A survey of the literature pertaining to the effects produced by the action 

 of high pressure on solids at ordinary temperatures revealed a number of 

 outstanding discrepancies and uncertainties, some of which we were able to 

 eliminate by a critical study of the recorded results and of several series of 

 original observations. These discussions have been published and are ab- 

 stracted on a later page. 



Bombs Containing Water. — Closely allied to the investigation of those 

 problems in which pressure is of prime importance is another field, namely, 

 the investigation of the behavior of minerals in contact with water or aque- 

 ous solutions at moderately high temperatures (up to 500°). Vessels used 

 in such work must be capable of withstanding considerable pressures without 

 sensible leak in order to avoid loss of the volatile component. Here, again, 

 the technical difficulties are considerable, but many of them have now been 

 successfully obviated. A systematic experimental survey of this field has 

 been undertaken and considerable work in this direction has already been 

 accomplished ; but it has not proved possible yet to formulate from it any 

 definite conclusions of general application. 



Quarts and Other Forms of Silica. — Turning now from these investiga- 

 tions, which are mainly directed toward the perfection of the implements of 

 research and upon which the quality of the results attained very largely de- 



