IX 



THE WORK OF THE GEOPHYSICAL, LABOR- 

 ATORY OF THE CARNEGIE INSTITUTION 

 OF WASHINGTON 



By B. B. SOSMAN 



r I ^HERE are three methods of approach to the great 

 problem of rock formation. The first undertakes to 

 . M reproduce by suitable laboratory experiments some 

 of the observed changes in natural rocks. The second 

 seeks to apply the principles of physical chemistry to a 

 great body of carefully gathered statistics. The third 

 method of attack is like the first in being a laboratory 

 method, and like the second in seeking to apply existing 

 knowledge to the association of minerals as found in 

 rocks, but in its procedure differs widely from both. It 

 consists of bringing together pure materials under 

 measurable conditions, and thus in establishing by 

 strictly quantitative methods the relations in which min- 

 erals can exist together under the conditions of tempera- 

 ture and pressure that have the power to affect such 

 relations. 



It is to this third method of investigation of the prob- 

 lems of the rocks that the Geophysical Laboratory has 

 fteen devoted since its establishment in 1905. It has 

 proved entirely practicable to make quantitative studies 

 of the relations among the principal earth-forming 

 oxides (silica, alumina, magnesia, lime, soda, potash, and 

 the oxides of iron) over a very wide range of tempera- 

 tures. The resources of physics have proved adequate 

 to establish temperature with a high degree of precision 

 and to measure the quantity of energy involved in the 

 various reactions. The chemist has been able to obtain 

 materials in a high degree of purity, and to follow out in 

 detail the chemical relationships that exist among the 



