140 CARNEGIE INSTITUTION OF WASHINGTON. 



attention will be paid, throughout the series, to the chemistry of the lavas, and 

 a large number of new chemical analyses will be incorporated. Of these, up 

 to the present, about 50 have been made, and the whole series will contain 

 more than 100. The specific gravities of the rocks will also be investigated 

 systematically and fully. 



In the introduction to this first paper some questions of classification 

 (especially of the andesites and basalts) and of nomenclature are discussed. 

 The bulk of the paper deals with the rocks of Kohala and Mauna Kea. The 

 rocks of Kohala, the oldest volcano of the island, are shown to be referable 

 to four quite well-defined types: oligoclase andesite, olivine-oligoclase ande- 

 site, feldspar phyric basalt, and aphyric basalt. Their chemical characters 

 are shown by 9 new and 3 old analyses. The rocks of Mauna Kea are more 

 femic than those of Kohala and include: andesine andesite, andesine basalt 

 (two types), labradorite basalt, olivine basalt, and picrite basalt. There 

 are 10 new and 2 old analyses of these. Neither quartz-bearing nor nephelite- 

 bearing lavas are found at either of these two volcanoes. 



(492) Augite of the Alban Hills, Italy. H. S. Washington and H. E. Merwin. Am. 



Mineralogist, 8, 104-110. 1923. 



A description of one of the typical augites of the Alban Hills is given, with 

 determinations of its optical characters and a chemical analysis. It is shown 

 that there is considerable variation in the augite of this district. The paper 

 is one of a series in a study of the pyroxene group. 



(493) The system, calcium oxide-carbon dioxide. F. Hastings Smyth and Leason H. 



Adams. J. Am. Chem. Soc, 45, 1167-1184. 1923. 



Preliminary to the investigation of the natural conditions which may 

 have produced minerals such as cancrinite, spurrite, the dolomites, or other 

 minerals whose compound molecules appear to contain calcium carbonate 

 as one component, the system calcium oxide-carbon dioxide has been inves- 

 tigated. 



For this work a heavy-walled, water-cooled steel cylinder has been con- 

 structed, for experimentation up to pressures of about 1,000 megabars. 

 Within this container was placed a platinum-wound resistance furnace which 

 readily gave temperatures of about 1400° C. in the high-pressure range. The 

 pressures in every case were developed by the carbon-dioxide gas which filled 

 the free space within the container. The charges, held in small platinum 

 crucibles, were sufficiently small to insure fairly uniform temperature dis- 

 tribution. Electrical leads for the furnace and for the thermo-elements 

 were brought through the container walls in suitable soapstone plugs. 



The eutectic between calcium carbonate and calcium oxide lies at 1240° C=t 

 1° C, the corresponding pressure being 30,000 mm. ±300 mm. of mercury. 

 Microscopic examination of this mixture indicates the presence of about 

 equal amounts of oxide and carbonate. 



The melting-point of pure carbonate has not been attained, but at 1339° C. 

 and 779,000 mm. pressure, there fuses a mixture of carbonate and oxide 

 containing only about 0.3 per cent of oxide. 1340° must therefore be very 

 close to the true melting-point of the carbonate. 



The equation of the curve best representing the experimentally determined 

 dissociation pressures in millimeters, in terms of the absolute temperature 

 from 1 mm. to 30,000 mm. (the eutectic pressure), is found to be 



Log v= -11355/r -5.388 Log T-|- 29.119. 

 The values of Log p plotted against 1/T do not deviate greatly from the best 

 representative straight line which may be drawn through the points deter- 

 mined by the data up to the eutectic point where fusion takes place. Above 



