H. A. Daly — Secondary Origin of Certain Granites. 193 



Since the compositions of the hornblende, biotite and soda- 

 bearing orthoclase are not known, the chemical analyses can- 

 not be calculated from Table II. Direct chemical analyses of 

 types Nos. 1 and 7 in Table II have been made by Professor 

 Dittrich, of Heidelberg, and are recorded in Table III. 







Table 



III. 





SiO, 



Ti0 2 



Al O 







1. 



._ 51-920 



•83 

 .. 14-13 



2. 



71-690 



•59 

 13*29 



Fe 2 3 







.. 2-97 



•83 



FeO 



MnO 



MgO 



CaO 



Na,0 ...... 



KO 







.. 6-92 

 ._■ '14 

 .. 8-22 

 _. 11-53 

 .. 1-38 

 •47 



4-23 

 •09 

 1-28 

 1-66 

 2-48 

 2-37 



H 2 (below 

 H 2 (above 

 PO, 



110 c 

 110° 



C.)._- 



C.) ... 



•10 



.. 1-07 



•04 



•14 

 1-31 



•07 



CO, 







•06 



•13 













1. 



99-78 100-16 



Sp.gr 3-000 2-773 



Normal un acidified gabbro from sill about eleven miles east 



of the Movie sill. 



2. Acid rock fifteen feet from upper contact of the Moyie sill. 



The rock of col. 2 belongs to the granite family. The 

 silica is normal (higher in types of cols. 5 and 6, Table II), 

 but the total of the alkalies is extraordinarily low, namely 4'85 

 per cent, or -76 per cent lower than the total of the potash and 

 soda in the least alkaline among the twenty-six types of granite 

 analyses selected for Rosenbusch's "Elemente der Gesteins- 

 lehre." The comparatively high content of lime is probably 

 to be referred to a not unimportant mixture of lime feldspar 

 and alkaline feldspar in isomorphous relation, as well as to a 

 small amount of secondary epidote. 



Col. 1 shows the gabbro to be a normal type in some respects, 

 but the high content of silica and relatively low content of 

 alumina and soda are abnormal for gabbro. These features 

 are partly due to the predominance of hornblende over feld- 

 spar and to the presence of free quartz. It can be seen by 

 inspection of cols. 1 and 2, Table II, that the gabbro at the 

 bottom of the Moyie sill would give an analysis very close to 

 that of col. 1, Table III, which represents a good type of the 



