20 CARNEGIE INSTITUTION OE WASHINGTON. 



during the year by the Institution, namely, No. 157, "High Temperature Gas 

 Thermometry," and No. 158, "The Methods of Petrographic-Microscopic 

 Research." The purpose of the first of these was to give an account of the 

 apparatus and methods for accurate measurement of the critical tempera- 

 tures incident to mineral combinations; and the object of the second is to 

 place, so far as practicable, microscopic study of minerals upon a quantita- 

 tive basis. Attention has hitherto been called to this characteristic feature of 

 the investigations of the Geophysical Laboratory, which is a characteristic 

 feature of all of the advancing sciences. The work already accomplished 

 demonstrates the practicability of achieving this object for the science of 

 mineralogy. This advance requires that special attention be given to accu- 

 rate measurements of high temperatures and high pressures, as well as to 

 their simultaneous effects upon mineral constituents. Much study, therefore, 

 continues to be given by the Laboratory staff to the development of effective 

 apparatus and technique for the measurements essential in this work. 



Special attention is called in the Director's report to extended studies on 

 quartz and other forms of silica, which is the most widely diffused ingredient 

 in rock masses; to further experiments on the conditions of association of 

 the three oxides, lime, alumina, and silica, which in addition to being the com- 

 monest components of igneous rocks are also incidentally the three principal 

 ingredients of the so-called Portland cement ; to mineral sulphides, which are 

 often of great economic importance ; and to mineral and rock densities. 



Perhaps the most interesting of the more recent investigations of the Lab- 

 oratory are those of the physics and chemistry of active volcanoes under- 

 taken tentatively a year ago and pursued with very gratifying success during 

 the past summer. It has proved practicable for members of the staff to 

 descend into the crater of Kilauea and to collect considerable quantities of 

 gas as it emerged from the liquid lavas of the crater. Specimens of gases 

 were collected in glass tubes without contamination from the air, and these 

 have been brought to the Laboratory at Washington for detailed study. 

 There seems little reason to doubt that the phenomena of vulcanism will be 

 ultimately revealed by the methods, apparatus, and technique developed by 

 the staff of the Laboratory. 



Naturally a department devoted to historical research is chiefly concerned 



with the preparation of publications, and these latter for the department in 



question may be classified under the head of reports, aids, 



Department of anc j guides concerning materials relating to American his- 



ills tori C3l i"\escflrcn. 



tory and under the head of textual publications of docu- 

 ments. Under the first head attention may be called to Prof. Marion D. 

 Learned's "Guide to the Manuscript Material Relating to American History 

 in German State Archives," No. 150 of the publications of the Institution, 

 which has appeared during the year. Two other volumes, namely, publica- 

 tion No. 90A, "Guide to the Materials for American History, to 1783, in the 



