Geology and Mineralogy . 231 



of the world progresses, be found to exist in other regions as 

 common types occurring in enormous masses. l. p. v. 



10. The Viscous vs. The Granular Theory of Glacial Motion • 

 by Oswint W. Willcox. Published by the author. Price, post- 

 paid, 30 cents. Long Branch, New Jersey, pp.23, 1906. — The 

 summary of contents, as stated by the author, is as follows : "A 

 leading argument against the viscous theory of glacial motion, 

 based on the assumption that crystalline character is incompatible 

 with viscous fluidity, is shown to be without force in view of the 

 existence of crystalline liquids." 



"An exact definition of fluid, viewed as a datum of mechanics, 

 is given, and it is pointed out that certain glacial phenomena are 

 rendered intelligible by the use of this definition, and are not, as 

 has been held, incompatible with a viscous nature of ice." 



" It is pointed out that advocates of the granular theory of 

 glacial motion have ignored a vital question : the relation 

 between the rates of accumulation and dispersal of free energy 

 within a glacier." 



" It is shown that if the conditions postulated by the granular- 

 ists actually prevailed in nature, the forward advance of a glacier 

 would be incredibty limited." 



In this paper, as the preceding paragraphs indicate, Dr. Will- 

 cox brings a number of interesting facts and theories from 

 organic chemistry, mechanics, and technological practice to bear 

 upon the old problem of the nature of glacial motion. While 

 this treatment from another viewpoint is undoubtedly valuable 

 many will doubt the final statement quoted, and ask to what 

 extent such apparently opposing principles may cooperate. J. b. 



11. The Decomposition of the Feldspars • by Allerton S. 

 Cushmak and Prevost Hubbard, U. S. Department of Agricul- 

 ture. Office of Public Roads. Bulletin, No. 28, pp. 29, figs. 6, 

 1907. — Those interested in chemical geology should have their 

 attention called to this important paper, as well as a previous one 

 by Mr. Cushman, since they are published in a series of Govern- 

 ment reports which geologists might easily overlook. 



The results of the investigations may be summarized as follows: 

 Water acts immediately upon finely powdered feldspars. The 

 reaction does not proceed far, however, owing to the clogging 

 effect of the unremoved decomposition products. The insoluble 

 hydrated aluminum silicate holds tenaciously the soluble alkalies 

 with the result that the analysis of a solution obtained by extract- 

 ing or leaching a weighed quantity of powdered feldspar would 

 fail to measure the extent to which decomposition had taken 

 place. The authors consider that these absorbed soluble alkaline 

 silicates are undoubtedly available for plant food and indicate 

 that the common methods of making soil analyses, by leaching 

 with dilute acids, and dividing the isoil on that basis into avail- 

 able and unavailable portions, are in error. 



The authors find, however, that the decomposition of feldspar 

 powder can be made to go farther by mechanical abrasion in the 



