ABLTRACTS: GEOLOGY 165 



to 70 or 79 feet above sea level, and except where removed or uncovered 

 by erosion are buried under later gravel deposits, having a maximum 

 thickness of 120 feet. F. H. M. 



GEOLOGY. — Nitrate deposits. Hoyt S. Gale. U. S. Geological Survey 

 Bulletin 523. Pp. 36. 1912. 

 This paper consists of a short summary of the natural occurrences of 

 nitrate salts kno^\^l in the United States. The descriptions are chiefly 

 compiled from the references to such occurrences found scattered 

 throughout geologic and other literature, the use of such deposits as a 

 source of nitrate for the manufacture of powder during war time having 

 been a frequent source of comment. Some new descriptive data by the 

 author and analyses from materials collected in the field are also in- 

 cluded. The article contains a review chiefly by quotation, of the 

 theories concerning nitrification as bearing on the probable origin of 

 such deposits. H. S. G. 



GEOLOGY. — The Jurassic flora of Cape Lisburne, Alaska. F. H- 

 Knowlton. U. S. Geological Survey Professional Paper, 85-D. 

 Pp. 55, with sections. 1914. 

 The Jurassic section of Cape Lisburne, to which the name Corwin 

 formation has been given, reaches the thickness of over 15,000 feet. 

 So far as at present known the fossil flora is uniformly cUstributed 

 throughout, and embraces 17 species, only one of which is described as 

 new. This flora is compared with known Jurassic floras of various 

 parts of the world, and the conclusion is reached that it is not only 

 •undoubtedly Jurassic in age — which had previously been questioned — 

 but belongs either in the upper part of the Middle Jurassic or Bro^vn 

 Jura, or the extreme lower part of the Upper Jurassic or White Jura — 

 that is to say it is probably not older than the Bathonian, and certainly 

 not younger than the Oxfordian. Several pages are devoted to a dis- 

 cussion of the geographic range of Jurassic floras in general, their means 

 and avenues of dispersal, and the probable climatic conditions that pre- 

 vailed in Alaska at the time this flora flourished there. F. H. K. 



GEOLOGY. — The origin of colemanite deposits. Hoyt S. Gale 

 L^. S. Geological Survey Professional Paper 85-A. Pp. 9, 1913. 

 Colemanite, the borate of lime from which practically all commercial 

 borax and boric acid is derived in this country at the present time, has 

 been discussed by various writers, but its origin has always been ascribed 

 to the dessication of saline or alkaline waters, usually as deposits of 



