GEOPHYSICAL LABORATORY. 9I 



to be redetermined with considerable accuracy, the work upon the high- 

 temperature gas scale up to 1,200° is finished and the accuracy of the deter- 

 mination very satisfactory. After remounting the apparatus, which is very 

 complicated, this investigation will be continued in the new laboratory to 

 temperatures considerably higher than 1,200°, and, if successful, as there 

 is now considerable reason to believe it will be, will contribute greatly to 

 the exactness of all temperature measurements in that, for mineral formation, 

 most important region lying between 1,200° and 1,600° C. 



Action of Water upon the Minerals. — Another investigation, which was 

 foreshadowed in the last annual report from the Geophysical Laboratory, is 

 the action of water upon mineral and rock formation, to which the geolo- 

 gists attach the utmost importance and upon which experimental measure- 

 ments are still almost entirely lacking. Preliminary work in this direction 

 has been undertaken in closed bombs within which great pressure can be 

 developed, using several different mineral combinations and with considera- 

 ble variations of the physical conditions, pressure, and temperature. But it 

 is hardly fair to offer even a preliminary report upon such a complicated 

 subject with the data so far at our disposal. The experiments are difficult, 

 require much time and labor, both in preparation and in execution, and the 

 experimenter is frequently led far afield by the complete absence of any 

 trustworthy experience in such work. One conclusion of importance appears 

 to follow from our experimentation so far, namely, that the activity of hot 

 w-ater under high pressure as a "mineralizing" agent has been very greatly 

 overestimated, unless — and here lies the key to the apparent activity of water 

 in nature which geologists and mineralogists have uniformly recorded — the 

 water contains substances, like the soluble alkaline salts, in solution. Its 

 activity in contact with the more stable minerals is then enormously increased. 

 It may be fairly inferred that the waters of nature, the chemical activity of 

 which is very apparent in niany formations, were charged to a high degree 

 with these soluble salts. The problem as it now stands, after these prelimi- 

 nary trials, is much more complicated than has heretofore been suspected, and 

 is therefore one step farther removed from prom.pt and final solution. 



Mineral Solutions. — Our established lines of investigation in mineral solu- 

 tions have been continued during so much of the year as the Laboratory 

 remained undisturbed in its old quarters, but the equipment of the new build- 

 ing is not yet sufficiently advanced to enable us to resume it. The more 

 recent work has been confined to studies of the alumina-silica series, includ- 

 ing sillimanite in its various physical forms, the metasilicates of calcium and 

 magnesium in which diopside occurs and w^hich is now nearly complete and 

 ready for publication, and, finally, some more or less prelimi^ .--y work in 

 adjacent portions of the lime-magnesia-silica 3-component systc.i, in which 

 an investigation of tremolite is perhaps the most important and farthest 

 advanced. 



