90 THE CANADIAN NATURALIST. [Vol. ix 



The principles presented lead to the following subdivisions in 

 an arrangement of crystalline rocks, exclusive of the Calcareous 

 and Quartzose kinds. Since leucite is a potash-alumina silicate, 

 like orthoclase and raicrocline (it affording twenty per cent, or 

 more of potash), it is here referred to the same group with the 

 potash feldspars ; nephelite, sodalite and the saussurites being 

 eminently soda-bearing species, they are included with the soda- 

 lime feldspars (anorthite to albite). This reference for litholo- 

 gical purposes of these minerals is sustained by their resemblance 

 to the feldspars in constituents, and also in the quantivalent ratios 

 between the alkalies alumina and silica, this ratio being in leucite 

 1:3:8, as in andesite, and in sodalite and nephelite 1 : 3 : 4, as 

 in anorthite. The term potash feldspar, as used in the headings 

 below, is hence to be understood as covering orthoclase, micro- 

 cline and leucite ; and soda-lime feldspar, as including the tri- 

 clinic feldspars from anorthite to albite, and also nephelite, 

 sodalite and the saussurites. 



The arrangement is as follows. In the first series, the rocks 

 graduate into kinds which are all feldspar, and into others that 

 are all mica ; and yet the amount of pottish present is approxi- 

 mately the same. 



I. The Mica and Potash Feldspar Series: including 

 Granite, Granulite, Gneiss, Protogine, Mica schist, etc., Felsyte, 

 Trachyte, etc., and the Leucite rock of Wyoming. 



II. The Mica and Soda-Lime Feldspar Series : includ- 

 ing Kersantite, Kinzigite ; and the nephelitic kinds Miascyte, 

 Ditroyte, Phonolyte, etc. (These nephelitic kinds belong almost 

 as well in the preceding series. 



III. The Hornblende and Potash Feldspar Series : 

 including syenyte (with Quartz-syenyte), Syenyte gneiss, Horn- 

 blende schist, Amphibolyte, Unakyte (this last containing epidote 

 in place of hornblende) ; and the nephelitic species Zircon-Syen- 

 yte, Foyayte. 



IV. The Hornblende and Soda-Lime Feldspar Series: 

 including Pioryte (with Propylyte), Andesyte, Labradioryte (or 

 Labrador-dioryte), etc., and the saussurite rock, Euphotide. 



V. The Pyroxene and Potash Feldspar Series: includ- 

 ing Amphigenyte. 



VI. The Pyroxene and Soda-Lime Feldspar Series : 

 including Augite-Andesyte, Noryte (Hypersthenyte and Gabbro 

 in part), Hypersthenyte (containing true hypersthene), Doleryte 

 (comprising Basalt and Diabase), Nepheliuyte, etc. 



