THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 9 



attitude of the gneisses with respect to the central eruptive, as 

 facts discordant with this conception have repeatedly been brought 

 to light. If there is any single structure which may be said to per- 

 vade the whole Adirondack area, it is rectilinear, not circular in 

 character. The trend toward this more modern generalization is 

 seen as early as 1895; Smyth then pointed out (1895, page 264) 

 that the parallel belts of associated gneisses and limestones on the 

 northwest flank of the Adirondacks extended long distances parallel 

 to their strike, that is, northeast-southwest; and in the same year 

 Kemp (1895, pages 242-43) emphasized the fact that this linear 

 structure occurs also in the interior of the mountains. These dis- 

 coveries thus afford a modification of the quaquaversal hypothesis 

 of Van Hise, though admitting in general the nuclear character of 

 the central eruptives. 



To confine our attention only to the northwest border, however, 

 it is noticeable that the chief problems which confronted those who 

 worked in the Adirondacks after the days of Van Hise's traverse, 

 were concerned less with the larger structural features of the moun- 

 tains than with the more intimate relationships exhibited by the vari- 

 ous rock types with each other. Questions of origin and history 

 came into special prominence. Gneisses, meaning broadly sili- 

 ceous rocks, have always been more or less sharply differentiated in 

 the literature from limestones which are nearly everywhere asso- 

 ciated with them. Concerning such calcareous formations, there 

 has been of late years scarcely any divergence of opinion. The 

 igneous origin of the Adirondack limestones, at an earlier date seri- 

 ously entertained by prominent geologists, has long since been dis- 

 proved and is of historic interest only. Nevertheless, in justice to 

 Emmons and those who shared his views, it must be admitted that 

 the evidence presented by the limestones, considered in itself, is ob- 

 scured by no small amount of ambiguity ; but the sedimentary origin 

 of the limestones is now thought to be sufificiently established. 



With the gneisses, on the other hand, the case is somewhat dif- 

 ferent. From the earliest days diverse rocks whose field relations 

 were obscure or whose origin uncertain, have been relegated to this 

 catch-all class, and the task of later investigators has been primarily 

 to decipher this complex, and to determine which were igneous and 

 which sedimentary, which intrusive and which country rock. To 

 this end, at a time when the gneisses were all thought to be sedimen- 

 tary. Prof. C. H. Smyth, jr (1898, pages 490-92) considered the 

 nature and genetic significance of the streaks and irregular patches 

 of amphibolite so commonly associated with and surrounded by the 



