332 Scientific Intelligence. 



in a region will presumably increase and the additional small 

 circles will finally give something of the tinted effect. In addi- 

 tion, in the more sparsely settled districts there is a lack of 

 complete record of small shocks away from the centers of popula- 

 tion and a consequent tendency for the larger circles to cluster 

 around the inhabited districts. For these reasons it might have 

 been advantageous to have supplemented the present detailed 

 maps with more comprehensive ones in which curves and tints 

 should bring out the lines and places of greatest seismic disturb- 

 ance. To a slight extent this has been done. The author reiter- 

 ates his previous conclusions in regard to the independence of 

 the great majority of shocks from volcanic centers, even in vol- 

 canic regions. The data also bring out the poverty of earth- 

 quakes over the geologically undisturbed portions of the crust and 

 their association, on the contrary, with great fault zones, lines of 

 folding, regions of great relief and geosynclines. They are evi- 

 dence, in brief, of the internal forces of the world still at work. 



In regard to the more highly inferential portions of the work ; 

 the author assumes the truth of the extreme views held chiefly 

 by certain European geologists in regard to former land masses 

 covering the greater portions of the present ocean basins and 

 known as the Africano-Brazilian continent, the North Atlantic 

 continent, etc., and discusses the relation of the earthquake zones 

 to the fragmentation and foundering of these supposed land 

 masses. It need hardly be said that much of this is highly 

 hypothetical and that according to the charts in the back of the 

 volume there was apparently no room for the ocean waters during 

 Mesozoic time. On the whole, however, the volume is a most 

 valuable contribution to that branch of geology which deals 

 with earthquakes. j. b. 



8. The Copper Deposits of the Clifton- Mot end District, Ari- 

 zona ; by Waldemar Lindgren. U. S. G. S. Professional 

 Paper No. 43. 365 pp., 25 pis., 1 9 figs, in text.— The Clifton 

 copper district is second onty to Bisbee in rank among the cop- 

 per districts of Arizona, its production for 1903 amounting to 

 53,400,000 pounds of copper. The present paper is a complete 

 and detailed discussion of the ore deposits of this area and con- 

 tains, particularly in its discussions of the contact metamorphism 

 shown in the district and of the secondary enrichment of the ores, 

 important contributions to the subject of economic geology. 



The underlying rocks of the quadrangle • are schists and a 

 granite of pre-Cambrian age. Upon these rest unconformably a 

 series of Paleozoic sediments, of nearly a thousand feet in thick- 

 ness, composed chiefly of limestones, with some interbedded quartz- 

 ites and shales. Above this series are found in certain sections 

 several hundred feet of sandstones and shales which have been 

 assigned to the Mesozoic Intruded into all of these rock types 

 in the form of stocks, dikes, sheets and laccoliths are a series of 

 igneous rocks ranging in type from diorite-porphyries to granite- 

 porphyries. These intrusions probably occurred in early Ter- 



