A. Geikie—Archeean Rocks of the Wahsatch Mts. 365 
these facts, one might suppose, would be that the granite is 
later in date than the rocks overlying it. Mr. King admits 
that the granite had been undoubtedly the center of local met- 
amorphism, but this change he regards as “ strictly mechanical 
and not to be mistaken for the caustic phenomena of a chemi- 
cally energetic intrusion.” (p. 45). How he would discriminate 
between a mechanical and chemical cause producing precisely 
the same ultimate effect he does not explain. Had he not been 
firmly convinced that all the granite must be Archean he 
would hardly, I venture to think, have penned that sentence. 
wo pages farther on he admits that round the granite mass 
the Carboniferous limestones have been invaded by igneous 
dikes, and these rocks (named granite-porphyry by Zirkel), he 
asserts to be “middle-age porphyries, not to be confounded 
they be “middle age,” or rather on what grounds are we to 
Separate them from the neighboring granite? Not a single 
reason is given save the obvious one that when a geologist has 
made up his mind that a granite is Archean he cannot of 
course admit that it sends out ramifications into overlying Pale- 
ozoic rocks. Yet the natural tendency of any unbiased ob- 
server must, I should think, be to connect these surrounding 
ne argument given by Mr. King for the antiquity of the 
granite is that it does not send out dikes into the overlying 
Tocks, (p. 48). But, as he himself is no doubt well aware, the 
veins or dikes which penetrate the rocks around a granite boss 
are not always themselves granite. They very commonly take 
the form of his “ granite-porphyry.”’ 
