43 



of that region. The relations of the granite here referred to 

 the Huronian system, to the Naugus Head series, have been dis- 

 cussed (ante, p. 19). It can scarcely be doubted that it 

 overlies this ancient series, and belongs to a newer system. 

 It is associated in some part of its distribution with every 

 member of the Huronian series, and in all cases the indications 

 are plain that the granite is the older rock. It has been set 

 down by all observers as the oldest rock in this region, and this 

 view is abundantly justified (except as regards the Naugus Head 

 series), not only by its generally coarsely crystalline aspect and 

 the great disturbance and almost complete absence of stratifica- 

 tion which it everywhere exhibits, but also by the general fact 

 that it cuts, as an exotic, all the other members of the Huronian 

 system. In fact, it pierces, in its well-nigh universal extrav- 

 asation, every rock in this region, save the Naugus Head 

 series and the newer uncrystallines. In its geographical dis- 

 tribution we have a strong indication that the granite belongs 

 to the Huronian system ; for it is co-extensive with that system, 

 and does not occur beyond its limits. And it will be shown 

 farther on that its lithological relations point indubitably to the 

 same conclusion. But its petrology makes it clear that, if the 

 granite is referred to the Huronian series, it must be regarded 

 as the lowest, and hence the oldest member of that series. It 

 appears, in fact, to be the foundation of the Huronian system 

 in Massachusetts. 



It will not have escaped observation that this so-called Hu- 

 ronian granite has, as a whole, a decidedly Laurentian aspect ; 

 and some geologists would probably refer it to that great funda- 

 mental system. Indeed, the granite of the Newbury belt, de- 

 scribed above, is one of the rocks associated with the serpentinic 

 limestone of that town, and referred by Dr. T. Sterry Hunt 

 to the Laurentian, as noticed (ante, p. 25) . The most character- 

 istic rock of the Laurentian system, it is well known, is a 

 firm, coarse, granitoid, and, to the eye, frequently un- 

 stratified gneiss, composed chiefly of orthoclase and quartz, 

 with little hornblende and less mica, — a description which 



