Geology and Natural History. 157 



SCIENTIFIC INTELLIGENCE. 



I. Geology and Natueal Histoey. 



1. United States Geological Survey. — The following publica- 

 tions have recently been received: 



Professional Paper No. 11. — The clays of the United States 

 east of the Mississippi River; by Heinrich Ries. 287 pp., 9 

 pis., 11 figs. The origin of clay, its composition, varieties and 

 uses is discussed and its geologic distribution described. The 

 greater part of the paper is taken up with a detailed description 

 and discussion of the clay deposits and the clay industry of the 

 states east of the Mississippi. 



No. 12. — Geology of the Globe Copper District, Arizona; by 

 F. L. Ransome. 165 pp., 27 pis., 10 figs. 



The oldest rocks of the Globe district are crystalline schists of 

 pre-Cambrian age, which, together with intruded masses of gran- 

 itic rocks, form the core of the Pinal range. Upon these schists 

 lie a series of shales, conglomerates and quartzites, varying in 

 thickness from 500 to 800 feet, which have been assigned to the 

 Cambrian. Overlying these is a series of limestones with a 

 maximum thickness of about 400 feet. They range in age from 

 Devonian to Upper Carboniferous. In addition to the sedimen- 

 tary rocks there are large masses of diabase, which were intruded 

 chiefly in the form of silts between the sedimentary beds. Later 

 still, another volcanic eruption brought extension masses of dacite 

 into the region. 



The structure and topography of the region is largely depen- 

 dent upon the great number of faults found in the district. Mr. 

 Ransome says, " Probably few equal areas of the earth's surface 

 have been so thoroughly dislocated by an irregular network of 

 normal faults, and at the same time exhibit so clearly the details 

 of the fractioning." 



Mining in the district was commenced in 1874. The early 

 work was done on silver and gold deposits, the copper ores which 

 are the predominant ones to-day not having been seriously worked 

 until after 1881. Since then the quadrangle has produced approx- 

 imately 120,000,000 pounds of copper. 



The copper ores belong to two mineralogical classes: (^oxi- 

 dized ores being mostly cuprite, malachite or chrysocolla, and (2) 

 sulphide ores being mostly pyrite and chalcopyrite. The first 

 group has furnished the major part of the ore up to the present. 

 The ore bodies exhibit various forms and may be classed as (1) 

 lodes, (2) masses in limestone and (3) irregular mineralization of 

 shattered or permeable rocks. The lodes are usually simple veins 

 occupying fault fissures. The important ore bodies are those in 

 the limestone. These are usually rudely lenticular in shape, and 

 lie roughly parallel to the bedding of the rock occurring scat- 

 tered irregularly through it. They are usually either in a prom- 



