abstracts: geology 135 



usual way, by extrapolating the curve of temperature and thermal 

 electromotive force. These results now require to be corrected by the 

 amount of the difference between the old temperature scale and the new, 

 which makes it necessary to recalculate the existing temperature data 

 of this laboratory in terms of the new gas scale. This paper presents 

 a summary of the values resulting from this recalculation. 



Some of the European students of silicate solutions have encountered 

 difficulties in the determination of mineral melting-points which have 

 led to the belief that most or perhaps all minerals do not melt at a deter- 

 minable "point," but rather that the phenomena of melting extend 

 through a considerable temperature interval. Experimental evidence 

 is here offered, in the case of two of the typical minerals in question, 

 that this uncertainty was merely the result of the experimental method 

 employed. This is a matter of some importance, because the above 

 conclusion, if true, would necessitate a new system of definitions for 

 melting silicates. A. L. D. and R. B. S. 



GEOLOGY. — Geologic atlas of the United States, Folio No. 174, Johns- 

 town, Pa. W. C. Phalen. U. S. Geological Survey, Pp. 15, 

 with maps, sections, and views. 1911. Mineral resources of Johns- 

 town, Pa., and vicinity. W. C. Phalen and Lawrence Martin. 

 Bulletin U. S. Geological Survey No. 477. Pp. 142, with maps, 

 sections, and views. 1911. 

 The Johnstown quadrangle, embracing 228 square miles, is situated 

 in west-central Pennsylvania near the eastern escarpment of the Appa- 

 lachian Plateau. The rocks are entirely sedimentary and range in age 

 from Devonian (Catskill formation) to the Conemaugh formation of the 

 Pennsylvanian series of the Carboniferous. They have a thickness of 

 about 3200 feet and are bent into northeast-southwest folds. The 

 structure as worked out differs in some particulars, especially near Johns- 

 town, from the results obtained by the Second Geological Survey of 

 Pennsylvania. 



The mineral resources include coal, clay, shales, limestone, and cement 

 materials, building stone, paving block, concrete materials, glass sand, 

 and iron ore. Numerous analyses of these commodities are given with 

 the results of steam, coking, briquetting, cupola, producer-gas, and float 

 and sink tests of the coals. 



At least five coals, confined to a vertical interval in the Allegheny 

 formation, ranging from 150 to 200 feet, are locally workable. 



W. C. P. 



