EfeUM^, AND GENEKAL DISCUSSION. 



555 



The latter held that the foliation planes in all gneisses were the resulta 

 of stratification and proof of deposition from water — the sedimcnta 

 subsequently having been altered by subterranean heat. Those rocka 

 which had been classed aa primary, Lyell called hjpogene, dividing them 

 into an unstratified or plutonic series and an altered or metamorphic 



series. 



He also contended that "all the hypogcne strata, beautifully 

 compact and crystalline as they are, have once been in the state of 

 ordinary mud, clay, marl, sand, gravel, limestone, and other deposits 

 now forming beucath the waters."* 



Following the above views of Lyell we see Logan at the outset giving 

 the name "Metamorphic Series" to the older crystalline rocks, assum- 

 ing that the planes of foliation were stratification planes ; and stating 

 that the "syenitic gneiss" or granite possessed "an aspect inducing the 

 theoretical belief that they may be ancient sedimentary formations in 

 an altered condition." t Such a belief, if simply loolvcd upon as a the- 

 ory, to be proved or disproved, by the light of future evidence to be 

 carel^illy sought for, would not have done great harm; but such was 

 not the method of the Canada Survey, whose officers never took one 

 step toward ascertaining the correctness of their theoretical belief Yet 

 we find Logan declaring, in 1803, that the Geological Survey hnd 

 shown, in 1846, that the Laurentian consisted of "a series of meta- 

 morphic sedimentary strata underlying the fossiliferous rocks of the 

 province," Hunt, in 1855, making a similar statement. J 



One who carefully reads the reports of that survey can hardly fliil to 

 observe that the entire geology of the crystalline rocks was worked out 

 on the supposition that they were stratified, and that the laws of their 

 relations were those that Logan had employed in the study of coal- 

 fields, a difference in the dip or strike of the foliation being considered 

 suflEieicnt for the establishment of a new geological formation. No 

 examination seems to have over been made for the purpose of ascer- 

 taining the origin and history of the rocks in question. 



We will now proceed to examine, a little more in detail, the way in 

 which the Azoic or Laurentian rocks came to be divided into two groups 

 — the Laureutiau and Huronian. This division originated in the con- 

 founding by Logan of the basaltic volcanic rocks interbedded with the 

 Potsdam sandstone of Keweenaw Point with the basic or greenstone 



♦ Lyell's Principles of Geology, 1833, 1st ed., III. 367, 374, 376 ; 1834, 3d ed., 

 IV. 280, 281, 292; and all subaequeut editions of the Principles and Elements, or 



Manual, 



t Antct pp. 331, S32, 



X Ante, pp. 338, 342, 



\i 



