144 CARNEGIE INSTITUTION OF WASHINGTON. 



(34) Some lavas of Monte Arci, Sardinia. Henry S. Washington. Am. Jour. Sci. (4), 



36, 577-590. 1913. 



This extinct volcano was visited in October 1905, in connection with Grant 

 No. 95 from the Carnegie Institution of Washington. It has not been 

 described since 1857. It is shown that the volcano consists of a core of 

 rhyolite, Avith later flows of dacite, andesite, and trachyte, closing with 

 extensive sheets of basalt, in many respects resembling the nearby and better 

 known Monte Ferru. Detailed petrographic descriptions of the lavas are 

 given, together with seven complete analyses. An apparently new mineral 

 was found, which is to be further investigated. The paper is a preliminary 

 one, and the volcano is worthy of another visit and fuller study. 



(35) The determination of mineral and rock densities at high temperatures. Arthur 



L. Day, R. B. Sosman, and J. C. Hostetter. Am. Jour. Sci. (4), 37, 1-39. 1914. 



The existing and rather conflicting data on the volume change of rocks on 

 fusion are reviewed briefly. A method and apparatus is then described for 

 the determination of the specific volume of metals or of solid or fused sili- 

 cates from 200° to 1600°. The basis of measurement is the expansion of 

 artificial graphite, which was determined from 20° to 1500°. Volume curves 

 are given for tin, lead, and the eutectic of lead and tin. 



Measurements were made on quartz up to 1600°. The volume of quartz 

 increases more and more rapidly as 575° is approached. At this point the 

 inversion takes place to the high-temperature form, whose volume decreases 

 slightly with rising temperature. Between 950° and 1250° gases are given 

 off. Above 1300° the volume is increased greatly by the formation of 

 cristobalite. 



Granite shows the same form of curve as quartz. Above 500°, however, 

 it is not possible to obtain its true volume expansion because of the shat- 

 tering and permanent dilatation due to unequal expansion of the minerals 

 and to escape of gases. The same is true of crystalline diabase. 



The curve of glassy diabase can be obtained, however. The glass crys- 

 tallizes with contraction of volume at about 900°, then begins to fuse again 

 at about 1150°. On cooling, the liquid again crystallizes with contraction. 

 This behavior explains completely the results of Barus, which have been 

 widely quoted. A recalculation of his data on the basis of a redetermina- 

 tion of his fundamental volume show them to be in good agreement with 

 the new measurements. The bearing of these data upon the occurrence of 

 "floated" slabs of rock in the Palisade diabase is discussed. 



(36) Dichtebestimmungen bei hohen Temperaturen. Arthur L. Day, R. B. Sosman, and 



J. C. Hostetter. Neues Jalirb. 1914. (In press.) 



A German translation of "Densities at high temperatures" (Am. Jour. 

 Sci. (4), 37, 1-39, 1914). Reviewed under No. 35 above. 



(37) New crystaUine siUcates of potassium and sodium; their preparation and general 



properties. George W. Morey. J. Am. Chem. Soc. 1914. (In press.) 



Much work in the aggregate has been done on the action of water at 400° 

 to 500° on minerals (compare abstract No. 19), but so far with very little 

 really tangible result. The main reason for this lack of success is that the 

 investigators worked with too complicated systems and did not control con- 

 ditions with sufficient care. Accordingly it seemed desirable to examine, 

 under carefully controlled external conditions, the simplest silicate systems; 

 to discover, namely, what compounds form when silica is heated up with 

 potash or soda in presence of water, and to determine if possible the limits 



