90 REPORTS ON INVESTIGATIONS AND PROJECTS. 



In a word, then, some essential phase of every one of the proposed prob- 

 lems in Group i has been undertaken and a sufficient number of such meas- 

 urements made in each instance to demonstrate with convincing certainty 

 the practicability of the general plan. 



In a similar manner, though not to the same extent, the problems suggested 

 under Group 2 (minerals and rocks from aqueous solutions) have been taken 

 up and proved to be within the reach of laboratory resources, provided only 

 that adequate time can be given to such studies. It happens that apparatus 

 of a novel kind and difficult to build is required for such research, besides 

 which the reactions themselves proceed with exasperating slowness. 



The problems of Group 3 (the deformation of rocks) were undertaken in 

 a separate plant in charge of Professor Adams, of Montreal, and are not 

 properly included within this report. 



Group 4 (the constants of rocks) has also been taken up in the Geophysi- 

 cal Laboratory to the extent of the facilities at its disposal. Temperatures, 

 pressures, and densities have been studied, as already mentioned in connec- 

 tion with Group i. Measurements of conductivity and of expansion coeffi- 

 cient have not yet been attempted upon actual rocks because of the fact that 

 the plant thus far available did not include facilities for it ; but there is not 

 the slightest reason to believe that such measurements will prove as difficult 

 as many of those already undertaken. Specific heat and the latent heat of 

 fusion and inversion have been successfully measured for several typical 

 minerals at the temperatures of rock formation. 



The problems suggested by the distinguished group of petrologists (Adams, 

 Cross, Iddings, Kemp, Lane, Pirsson, Washington, and Wolff, in Year Book 

 No. 2) include all of those already mentioned, some others to which these 

 are an indispensable preliminary, and some which are still beyond the reach 

 of the present resources of chemistry and physics. Nine of these have been 

 touched upon in the work of the Geophysical Laboratory hitherto. 



Of chief interest in reviewing this work just at this time is perhaps the 

 fact that no single problem of those so far attempted has miscarried. Al- 

 though the resources of physics and chemistry have been severely strained 

 to meet these extraordinary conditions offered by the igneous rocks, it has 

 proved practicable to put the plan in operation and to test its productiveness 

 over a considerable portion of the field which was mapped out. 



The time involved in developing new methods and adapting old ones has 

 been considerable, but that was to be expected. 



In most cases there has been opportunity for the measurement of but a 

 single typical substance or group of substances in order to elaborate and con- 

 firm the method of procedure and establish the conclusion. The broad appli- 

 cation to minerals in general and rocks in all their multitudinous complexity 

 still remains to be made, and is a herculean task for a single laboratory to 

 undertake unaided. Our procedure has been mapped upon a kind of skeleton 

 plan which has served to demonstrate the practicability of satisfactory studies 

 of the minerals and rocks through reasonably complete measurements upon 



