Geology and Natural History. 395 



This agrees very closely with the approximate estimate given by 

 Violle (1893), viz.: 3500° C. The method here employed is that 

 used by the same authors in an earlier investigation on the 

 effective temperature of the sun (Phil. Trans., A., vol. clxxxv, 361, 

 1894). This consisted essentially in balancing the radiation from 

 a platinum strip against that of the carbon of the arc. Further, 

 taking 3300° as the temperature of the crater of the positive car- 

 bon, that of the negative carbon is found to be about 2400°. No 

 estimate is attempted of the temperature of the arc itself. — Proc. 

 Hoy. Soc, lviii, 24. Ji ^ Ji t 



10. Melting points of some of the metals. — S. W. Holman, R. R. 

 Lawrence and L. Barr have recently given the following deter- 

 minations of the melting points of several of the metals, which 

 they believe to be more reliable than previous data. The values 

 are based upon 1072° C. as the melting point of gold, as given by 

 Holborn and Wien. They are as follows : 



Aluminum . 660° 



Silver __._ 970° 



Gold [1072°] assumed 



Copper 1095° 



Platinum 1760° 



All of the samples experimented upon were of a high degree of 

 fineness except the platinum, which may have contained 0*5 p. c. 

 of impurity. The paper, from which the above data are quoted, 

 gives in full the method of experiment followed. Other papers 

 by S. W. Holman, also recently published in the Proceedings of 

 the American Academy, have the subjects : Calorimetry, methods 

 of cooling correction ; also Pyrometry, calibration of the Le Cha- 

 telier thermo-electric pyrometer. 



II. Geology and Natural History. 



1. Economic Geology of the Mercur Mining District, Utah y 

 by J. Edward Sptjrr, with introduction by S. F. Emmons. Six 

 teenth Annual Report of the United States Geological Survey, 

 Part II, pp. 343-454. (Author's abstract.) — The Oquirrh moun- 

 tains are one of the parallel ranges of the Great Basin, and the 

 first lying west of the Wasatch range and the Great Salt lake. 

 Close to the southern end of this range the Mercur mining dis- 

 trict is situated, in a well-marked topographical basin which has 

 been called the Mercur basin. The rocks exposed in the Mercur 

 basin consist of about 12,000 feet of strata, chiefly massive lime- 

 stones with intercalated calcareous sandstones and occasional 

 shale beds ; fossils from various points in this series show it to be 

 all of Carboniferous age. In the lower part there are intruded 

 sheets of quartz porphyry of two distinct varieties. With one 

 of these varieties, which has a distinct granophyric structure, all 

 of the ore deposits of the district are associated. In the produc- 

 tive region this porphyry is reduced to three sheets, averaging 



