Septembee 21, 1900.] 



SCIENCE. 



447 



Geology of Part of Sonora, Mexico,' by Mr. B. 

 F. Hill. Both gentlemen are post-graduate 

 students of Columbia University. 



The rocks described by Mr. Finlay were sent 

 by Mr. E. D. Self to Professor J. F. Kemp. 

 The nephaline syenite is a very light-colored 

 rock, containing, besides abundant nephaline 

 and an orthoclase, small patches of dark-colored 

 silicates. Under the microscope these are seen 

 to be segerine augite intergrown with horn- 

 blende, and accompanied by magnetite and 

 apatite. Titanite is abundant, with the faces 

 (1-2-3) well developed, and some zircon occurs. 

 The tinguaite associated with this syenite is a 

 holocrystalline porphyritic dike rock, with 

 large phenocrysts of orthoclase, twinned on 

 the Carlsbad law, tabular in habit, parallel to 

 the clinopinacoid. The ground mass which 

 gives the rock an even, dark green color, con- 

 sists of a felt of tiny blades of segerine and or- 

 thoclase. The segerines are at times grouped 

 together in bundles around small patches of 

 biotite. 



Mr. Finlay then briefly discussed the distri- 

 bution of similar rocks in the various portions 

 of the United States, and exhibited a very in- 

 structive series of comparative charts of the 

 chemical composition of the rocks examined 

 and those of allied groups, the charts being 

 constructed on the principles of the graphic 

 method devised by Professor Hobbs, as worked 

 out by Mr. Finlay. 



The second paper, that of Mr. Hill, also 

 treated of Mexican rocks, and the same geo- 

 graphical maps were employed to illustrate 

 both papers. Little has been written about the 

 coal-bearing rocks and their associated erup- 

 tives in the state of Senora, Mexico. The 

 work done by Professor Durable and his asso- 

 ciates has thrown considerable light on some of 

 the problems. 



In the district investigated are representa- 

 tives of nearly all the formations from the 

 Archsean granites to the Quarternary sands and 

 gravels. The most important division, how- 

 ever, is the Triassic. The slates, sandstones, 

 quartzites, etc., with coal seams, make up the 

 lower or Bananca division of the Triassic, 

 while an immense series of associated eruptives, 

 including andesites, dacites, tufis, aadesitic. 



conglomerates, etc. , is considered the upper di- 

 vision. To the series of eruptives the name of 

 Lista Blanca has been given. The Lista Blanca 

 has hitherto been considered post-Cretaceous. 



In addition to the pre-Cretaceous eruptives, 

 there are numerous intrusives and flows of 

 diorites, rhyolate, and basalt, and in one in- 

 stance, trachite. It is probable that these are 

 mostly of Tertiary age. The diorites exert a 

 very noticeable effect on the formation of the 

 ore bodies of the region. 



Specimens of all the eruptives were brought 

 to New York and studied by Blr. Hill, in thin 

 section, under the microscope. A series of 

 chemical analyses of the type rocks was made 

 and a very clear relation established between 

 the magmas of the different flows. The re- 

 mainder of the paper dealt with details on the 

 petrographio characteristics of the rocks. 



Both papers were discussed by Professor 

 Stevenson, Professor Kemp, Dr. Julian and 

 Dr. White. 



Theodore G. White, 

 Secretary of Section. 



DISCUSSION AND CORRESPONDENCE. 



ME. TESLA AND THE UNIVBESE — HUMAN 



ENERGY AND HOW TO INCREASE IT — 



HIS PHILOSOPHIZING QUESTIONED. 



Me. Nikola Tesla has written a long article 

 in the Century Magazine for June with the title 

 ' The problem of increasing human energy, with 

 special reference to harnessing the sun's energy. ' 

 The paper is profusely illustrated with impres- 

 sive cuts of electrical experiments which, at 

 first sight, seem convincing. Most readers of 

 the Century looked at the striking cuts and 

 glanced at some of the head lines of the article 

 such as ' Development of New Principle ' ; 

 ' Production of Immense Electrical Move- 

 ments '; ' The Earth responds to Man'; Inter- 

 planetary Communication now probable,' and 

 accepted the headlines on the testimony of 

 the cuts ; or else took it frankly for granted 

 that so long an article must certainly prove 

 a great deal. 



The present writer has lately gone over the 

 text of the article, pen in hand, and herewith 



