Sosman — Work of the Geophysical Laboratory. 257 



and the conditions of rock formation; alumina; mag- 

 nesia ; and lime. 



II. Two -component systems: silica-alumina, includ- 

 ing sillimanite and related minerals ; silica-magnesia, 

 including the tetramorphic metasilicate MgSi0 3 ; silica- 

 lime, including wollastonite ; the alkali silicates, par- 

 ticularly with reference to their equilibria with carbon 

 dioxide and with water ; ferric oxide-lime ; alumina-lime ; 

 alumina-magnesia, including spinel; and hematite-mag- 

 netite, a solid-solution series of an unusual type. 



III. Three-component systems: silica-alumina-mag- 

 nesia, completed but not yet published; silica-alumina- 

 lime, complete, including the compounds that enter into 

 the composition of portland cement; silica-magnesia- 

 lime, completed but not yet published, including, however, 

 published work on the diopside-forsterite-silica system, 

 and on the CaSi0 3 -MgSi0 3 series; and alumina-mag- 

 nesia-lime. 



IV. Four components: Si0 2 -Al 2 3 -MgO-CaO : the in- 

 complete system anorthite-f orsterite-silica ; Si0 2 -Al 2 3 - 

 CaO-Na 2 0: the series of lime-soda feldspars (albite- 

 anorthite), and the series nephelite (carnegieite)-anor- 

 thite; Si0 2 -Al 2 3 -Na 2 0-K 2 : the sodium-potassium 

 nephelites. 



V. Five components: Si0 2 -Al 2 3 -MgO-CaO-Na 2 0: 

 the ternary system diopside-anorthite-albite (haplo-basal- 

 tic and haplo-dioritic magmas). 



Fairly complete studies have also been made of the 

 mineral sulphides of iron, copper, zinc, cadmium, and 

 mercury, and the conditions controlling the secondary 

 enrichment of copper sulphide ores are now being inves- 

 tigated. In connection with the sulphide investigations, 

 the hydrated oxides of iron have been studied chemically 

 and microscopically and the results will soon be ready for 

 publication. 



Throughout the work the mere accumulation of bodies 

 of facts has been held to be secondary in importance to 

 the development of new methods of attack and the eval- 

 uation of new general principles, and the specific prob- 

 lems studied have been selected from this point of view. 



Volcano Researches. — A branch of the laboratory's 

 work that is of general as well as penological interest 

 is the study of active volcanoes. Observations and col- 

 lections have been made at Kilauea, Vesuvius, Etna, 



Am. Jour. Sci. — Fourth Series, Vol. XLVI, No. 271. — July, 1918. 



