BI^SUM^ AND GENEKAL DISCUSSION. 



559 



Since the two soriea could not be distinguished 



ciated, while the mctamorphic agencies were at work making over the 

 beds into the crystalline form iu which we mow see them. Similar re- 

 sults have here and there been produced, although not on so grand a 

 Scale, during the succeeding geological ages, as we see exemplified in the 

 veins and segregated deposits of later times, which are so well known 

 to thoso who have occupied themselves with the study of vein phe- 

 nomena. That these segregated masses of calcareous materials, which 

 occur as veins and which are often metalliferous, are the result of or- 

 ganic agencies, no one who has studied them with care has ever for a 

 mon:icnt supposed ; and, as has been already stated, we believe that all 

 the evidence is strongly in favor of the idea that the calcareous masses 

 of the Azoic are also deposits from aqueous solution without the inter- 

 vention of living organisms. 



Pursuing the investigation still further, it is seen that the efforts of 

 Logan to apply the principles of his stratigraphical geology to the crys- 

 talline rocks led naturally to the adoption of supplementary principles 

 in order to sustain the sedimentary character of the rocks and to aid 

 in their identification. 

 by palyoontological evidence, it became necessary to uphold the idea 

 that lithological characters could take the place of palajontological ones 

 as a basis for the arrangement of rocks in chronological order, and their 

 division into groups. But this required that a still more important 

 step bo taken, — namely, to insist that ail crystalline rocks were of 

 Azoic age and that all non-crystalline detrital ones were Pakicozoic or 

 later; and this principle is now openly or tacitly assumed in all work 

 in which the Canadian methods are followed. To say that crystallines 

 necessarily differ in geological age from the non-crystallines, is equiva- 

 lent to claiming that the crystalline lava that haa flowed from Vesuvius 

 is not of the same geological age as that of the ashes and mud which 

 preceded and followed its eruption ; for such we have found in some 

 districts to bo the exact relations of the older crystallines to the non- 

 crystallines. Furthermore, it is now known that fossils occur in Scan- 

 dinavia, Belgium, California, and elsewhere in crystalline rocks, 

 for instance, mnmonites in greenstones. 



In the application of their principles the, Canadian Survey found it 

 convenient to still further dilfcrcntiate the rocks that had been classed 

 with the Laurentian and the Huronian, and especially with the latter, 

 since these are in part eruptive, in part detrital, and in part probably 

 segregated deposits, so that their entire conformability with one another 

 could not be expected. The first to be thus separated were the coarsely 



as, 



