50 THE CANADIAN NATURALIST. [March 



have had the greatest share in originating the special names of 

 rocks. 



In striving to attend to what has been indicated as desirable 

 and necessary in any attempt at classifying rocks, it has appeared 

 to us most judicious to attach greatest weight to their various 

 characters in the following order : 1, origin ; 2, texture ; 3, 

 chemical composition ; 4, mineralogical composition ; and 5, 

 locality. If a system be required at all resembling those of other 

 branches of science, these characters might be allowed respectively 

 to determine the classes, orders, families, species, and varieties of 

 rocks. 



II. — CLASSES OP ROCKS. 



If we, at the present day, look around us, and ascertain, from 

 actual experience, what the methods are which nature employs in 

 producing rocks, we find that they result from the operation of 

 two very distinct agencies. On the one hand we may see in 

 difi'erent countries, widely separated from each other, streams of 

 melted matter issuing from volcanoes and solidifying to rocks on 

 their sides or at their feet, while on the other hand we may 

 observe, on every sea beach or river delta, sand and clay, the 

 debris of pre-existing crystalline masses or fragmentary strata 

 being gradually consolidated to new rocks. Exactly parallel to 

 these operations of nature are certain artificial processes at work 

 around us, the products of which are entirely analogous to the 

 two classes of rocks just indicated. We may stand before an iron 

 furnace and watch the steady stream of slag flowing from the 

 hearth into a large iron wagon, and there solidifying to a mass of 

 solid, sometimes crystalline rock; and we may also visit a stamp 

 mill where valuable metalhc particles are being extracted from 

 poor vein-stones, and find, in the slime-pits of the establishment, 

 banded layers of half solidified strata, requiring but a little time 

 to eflfect their perfect consolidation. 



These two means employed by nature in producing rocks have 

 been steadily recognized by the majority of geologists, and the 

 two classes which result have been indicated by a superabundance 



of names. Unstratified and stratified ; igneous and aqueous ; 

 eruptive and sedimentary; exotic and indigenous; primary and 

 secondary; (protogene and deuterogene;) crystalline and elastic; 

 massive and fragmentary; original and derivate, are all terms 

 which have been used for distinguishing these two great classes, 



