ABSTRACTS 



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PHYSICS.— The reflecting power of various metals. W. W. Coblentz. 

 Bulletin Bureau of Standards, Reprint 152. 1911. 

 The reflectivity of various substances is given including tungsten, 

 tantalum, molybdenum, chromium, antimony, tellurium, vanadium, 

 silicon, graphite, etc. The paper gives also (Note I) the thermoelec- 

 tric properties of molybdenum, (Note II) a method for the preservation 

 of silver mirrors, and (Note III) comments on radiation laws of metals 

 (see also Bull. Bur. Standards, Reprints 45 and 105). W. W. C. 



GEOLOGY. — Mineral resources of the Llano-Burnet region, Texas, 

 with an account of the pre-Cambrian geology. Sidney Paige. 

 Bulletin U. S. Geological Survey No. 450. Pp. 103, with maps, 

 sections, and views. 1911. 



The rocks of the region are: (1) pre-Cambrian schists, gneisses, and 

 granites, (2) Paleozoic sandstones, limestone, and shales, and (3) Cre- 

 taceous sandstones, clays, and limestones. 



The folded and faulted Pa'eozoic strata, which surround the pre-Cam- 

 brian area, are separated from the pre-Cambrian by a great unconform- 

 ity. The Cretaceous formations rest almost undisturbed with pro- 

 nounced unconformity on the Paleozoic rocks. 



The pre-Cambrian (Algonkian?) rocks have been divided into (1) 

 the Packsaddle schist, predominantly basic, including amphibolite and 

 mica schists and old basic intrusive rocks; (2) the Valley Spring gneiss, 

 including quartzites or their derivatives, light-colored mica schists, 

 and acidic gneisses; (3) a very coarse-grained pink granite; (4) all other 

 granitic rocks. 



The granite cuts the schist as batholiths, dikes, and sills, and, in peg- 

 matitic phase is found in minute veinlets and in huge dikes :ni<l sheets. 

 There are all gradations between granite and schist. 



In some localities the contacts between schists and dikes are sharp; 

 at others the temperature of the intruding mass was so high that 



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