JUXE 20, 1913] 



SCIENCE 



957 



cited from the treatises of Slialer and Picker- 

 ing. 



In conclusion, let me remark that even 

 though we can not go to the moon to see for 

 ourselves what its temperature may be, or 

 whether gravitation acts there as here, or 

 what may be the power of the sun's unabsorbed 

 radiation, we are gifted with reason and can 

 form for ourselves just conclusions from ob- 

 served facts. Otherwise all astrophysics 

 would be impossible. 



Frank W. Very 



Westwood Astrophysical Observatory, 

 May, 1912 



THE OBE DEPOSITS OF WESTESN UNITED 

 STATES 



Amongst the valuable publications issued 

 by the United States Geological Survey is Mr. 

 James M. Hill's Bulletin 507 with the mis- 

 leading title " The Mining Districts of the 

 Western United States," as it deals solely with 

 the metalliferous mining districts. These dis- 

 tricts are grouped and numbered in each one 

 of the 13 states considered, and their distribu- 

 tion is shown upon 14 maps. The text gives 

 for each district its chief rocks and metallifer- 

 ous products, the publications of the Survey 

 relating to each one, and the distance and di- 

 rection of the nearest railroad station, etc. A 

 full index of all the districts mentioned con- 

 cludes the work, which should be in the hands 

 of every one interested in the ore deposits of 

 the west. 



To the general student of metalliferous de- 

 posits probably the most instructive portion of 

 the bulletin will be the " Geologic Introduc- 

 tion," by Professor Waldemar Lindgren, late 

 chief geologist of the Survey, present head of 

 the Department of Geology of the Massachu- 

 setts Institute of Technology, and one of our 

 foremost mining geologists. 



The evidences of the mineral wealth of the 

 Cordillera are found extending territorially 

 from the Pacific shore of United States east- 

 ward to western Texas and Oklahoma, and 

 geologically from the Pre-Cambrian to the 

 Recent. 



Since the deposition of ores is due to geo- 



logic agencies, it is pointed out that in the Cor- 

 dilleran region, where the rocks are horizontal 

 and undisturbed, the ore deposits are missing 

 or rare and poor. Again, while the metallites 

 occur mostly in the mountain ranges, yet 

 many, even of the highest, are barren; show- 

 ing that without other conditions, uplift, 

 faulting, and crushing of the rocks, and the 

 circulation of water through them does not 

 always produce ore deposits. 



Characteristic important deposits are where 

 Paleozoic sediments have been traversed by 

 moderate-sized eruptive masses of Cretaceous 

 or Tertiary age, the ores apparently being de- 

 posited shortly after the intrusion. A less 

 common but often rich deposit is found in 

 Tertiary andesitic and rhyolitic flows. 



All these deposits are believed to have been 

 formed by water solutions — largely in fissure 

 veins, chambers, and impregnations. The ores, 

 except gold and its tellurides, were apparently 

 originally deposited as sulphides of lead, iron, 

 zinc, etc., or oxides of iron ; but down to or 

 below the permanent water level, which varies 

 from a few hundred to 2,200 feet, these sulphides 

 have been oxidized to cerussite, hematite, cala- 

 mine, etc. Just below the oxidized zone occur 

 secondary sulphides, like chalcocite and silver- 

 bearing minerals, concentrated by the perco- 

 lating waters, often into bodies of great rich- 

 ness. 



Professor Lindgren gives under each state 

 a more detailed summary, but space does not 

 allow lis to continue further, and any one in- 

 terested can procure a copy by writing to the 

 director of the Geological Survey at Wash- 

 ington. 



Without intending to be captious it is sug- 

 gested that in future editions the term " ores " 

 should be used for " metallic ores " (see pp. 

 7-9), because there are no ores that are not 

 metalliferous. In the same way " mineral de- 

 posits " ought not to be used for metallites or 

 metalliferous deposits when the author in- 

 tends to exclude the memetallites or non-metal- 

 liferous deposits (see pp. 5-9). 



M. E. Wadsworth 



University of Pittsburgh 



