90 REPORTS OF INVESTIGATIONS AND PROJECTS. 



control of errors, and the quantitative determination of those constant factors 

 which enter into the problems through the changed laboratory conditions. 

 Some of this work is of sufficiently general interest to warrant publication, 

 but more of it is entirely preliminary and will apply in its proper place in 

 the work of the coming winter. 



Calorhnetry. — One of the more interesting examples of this preliminary 

 work, which has not been mentioned before in the reports from this Depart- 

 ment, is the preparation, now well advanced, for the exact study of the heat 

 involved in mineral formation and inversion and the specific heat of the 

 stable forms. As a physical problem, this is an attempt to apply calori- 

 metrical methods at the temperatures of mineral and rock formation ( i ,000° 

 to 1,500° C), a region so remote from the usual domain of calorimetry that 

 a very careful scrutiny and some modification of existing methods was inevi- 

 table. In fact, the question has been found so serious that the successful 

 solution of it has occupied one observer throughout the entire year. 



The phenomena heretofore investigated in the Laboratory have depended 

 primarily upon the establishment of the temperature which is characteristic 

 of certain reactions. It therefore constitutes a most important extension of 

 the scope of our observations to attempt to determine, in addition to the 

 temperature of a given reaction, also the quantity of heat which is involved 

 in it. To students of physics and chemistry the importance of obtaining this 

 additional information in the study of any group of substances will be 

 immediately obvious. Nor have mineralogists and geologists been unappre- 

 ciative of the need of measurements of this character ;'•' but in the absence of 

 all data, or of a physical laboratory devoted to problems of geological interest, 

 they have often found it necessary, for the proper discussion of field observa- 

 tions, to formulate working hypotheses involving definite quantities of heat 

 without any basis of experimental fact whatever. The contact relations 

 between wall rock and an intruding magma is a case in point. 



A preliminary report upon this calorimetric installation was prepared and 

 presented to the American Physical Society at its spring meeting in Wash- 

 ington, and reported in abstract in its Journal. f A brief resume of the 

 principal conclusions is included in the list of publications following (p. 94). 



Temperature Scale. — In much the same way the work upon the funda- 

 mental scale of temperatures, to which reference was made in the last annual 

 report, has passed through an important preliminary stage during the present 

 year and was reported briefly at the spring meeting of the National Academy 

 of Sciences and at the meeting of the Physical Society! a few days later. 

 Except for the expansion coefficient of the thermometer bulb, which requires 



* See report of President Van Hise upon the reasons for establishing a geophysical 

 laboratory, in Year Book No. 2. 

 t Phys. Rev., August, 1906, p. 137. 

 % Abstract in Phys. Rev., June, 1906, p. 531. 



