THE MONTEREGIAN HILLS 273 



lation also brings out clearly a point already mentioned, namely, 

 that in this rock the nepheline is much more highly altered than 

 in the essexite, as shown by the amount of kaolin present. This 

 kaolin, however, is not entirely derived from the alteration of the 

 nepheline, but appears as a haze all through the smaller feld- 

 spars, and hence in the extension of the results should be 

 assigned in part to the nepheline and in part to the feldspar. It 

 is of course impossible to measure the amount of kaolin present by 

 Rosiwal's method, occurring as it does distributed through the 

 sections in the form of extremely minute individuals. If, how- 

 ever, the amount of nepheline given by the Rosiwal measure- 

 ment be correct, namely 4.40 per cent. — and this of course 

 includes both the unaltered mineral and that filled with decom- 

 position products — then 1.84 per cent, of the kaolin has been 

 derived from the alteration of the nepheline. There will thus 

 remain 3.12 per cent, of the kaolin which has been derived from 

 and measured up with the feldspar. If this amount be added to 

 the feldspar found by calculation, it will increase the proportion 

 present to 77.15 per cent., which is within 0.09 per cent, of the 

 percentage of feldspar obtained by the Rosiwal measurement. 

 The norm of the pulaskite is found to be as follows : 



99.84 



Its position is, therefore, as follows : 



Class 1, persalane. 

 Order 5, canadare. 

 Rang 2, pulaskase. 

 Subrang 4, laurvikose. 



