796 



WHITMAN CROSS 



Manganese is recognized by calculating its ratio to ferrous iron and 

 establishing subsections of subgrad, one step farther than has been 

 necessary hitherto/ Fermor also calculates the position of lla 

 to the subsection of subgrad, but the small amounts of magnesia, 

 ferrous iron, and manganese (together but 1.99 per cent) make 

 it quite unnecessary to go beyond the precalcic subgrad. The 

 hypothetical garnet rocks. III and IV, fall in the Salfemanes, and 

 their classification is also calculated by Fermor to subsections of 

 subgrad. 



TABLE II 



Norms from Calcdxated Analyses 



The procedure by which Fermor provides a place for manganese- 

 rich rocks in the Quantitative Classification is, as just noted, quite 

 in harmony with the principles of the system, and on that score 

 its authors have no criticism to make. But in regard to the various 

 names proposed by Fermor, we must point out, in response to his 

 request, that all of them are quite unwarranted and cannot be 

 accepted since they are based on ''calculated analyses" derived 



' See Cross, Iddings, Pirsson, and Washington, "Modifications of the Quanti- 

 tative System," etc.. Jour. Geol., XXII (1912), 552-53. 



