abstracts: chemistri and geologi 235 



CHEMISTRY.— The determination of t<»tnl sulphur in india rubber. 

 C. E. Waters and J. B. Tuttle. Journal of [ndustrial and Engi- 

 neering Chemistry, 3: 734. 1911. Bulletin Bureau of Standards 

 8: No. 2. 1911. 



A comparative study of differenl methods already published and of 

 variations of these methods. The procedure finally adopted was essen- 

 tially that of Henriques, except that the nitric acid used to decompose 

 the rubber is saturated with bromine to ensure complete oxidation of 

 free sulphur to sulphuric acid. The methods were tester 1 1 >y using a large 

 uniform sample of rubber, as well as pure sulphur and a solution of sul- 

 phuric acid of known strength. C. E. W. 



GEOLOGY. — The Mount McKinley region, Alaska. Alfred H. 



Brooks. With description of the igneous rocks and the Bonnifield 



and Kantishna districts. L. M. Prindle. Professional Paper 



U. S. Geological Survey No. 70. Pp. 234, with maps, sections, 



and views. 1911. 



The Mount McKinley region is blocked out by the meridians 148° 



and 154° and parallels 61° and 65° 20' north, but the Alaska Range, 



which traverses the central part of this region is more specially here 



under consideration. The Alaska Range is a belt of rugged mountains 



trending northeast and east 50 to 60 miles wide and from 500 to 600 



miles long, of which Mount McKinley (20,300 ft.) is the highest peak. 



This range was practically unexplored until 1902, when most of the 



data were collected on which the following conclusions are based. 



Undifferentiated Paleozoic sediments, unconformably overlaid by a 

 great complex of volcanic, probably Jurassic, rocks (Skwentna group), 

 and these in turn unconformably succeeded by Middle Jurassic sedi- 

 ments (Tordrillo formation), occur in the eastern part of the range. 

 These rocks dip toward the axis of the range and form the eastern arm 

 of a broad synclinorium. In the western arm the Tordrillo formation 

 rests unconformably on a great series of Paleozoics which has been 

 subdivided into (1) Tatina group (Ordovician), (2) Tonzona group 

 (Silurian or Devonian [?| ), (3) Middle Devonian limestone, (4) Cant- 

 well formation (Carboniferous [?] ). The last, which rests unconform- 

 ably on the older rocks, has only been recognized in the northern part 

 of the range. Complex folding and profound faulting have taken place 

 along the inland (northern) front of the range, and in this some Kenai 

 beds (Eocene) are involved. Numerous stocks and dikes of granites, 

 diorites, and related rocks, probably of late Jurassic age, occur in the 



