in America and Europe. 271 
have however clearly established the views of Vanuxem and 
Keating as to the Primary age alike of the gneisses and the 
rather than Primary. It was described by Logan in 1847, as 
consisting of a lower group of hornblendic gneisses, without 
Superior, and by him distinguished from the Primary and 
classed with Transition rocks. 
bradoritic and hypersthenie rocks like those previously 
described by Emmons in the Primary region of northern New 
York, were, in 1853 and 1854, discovered and carefully studied 
‘n the Laurentide hills to the north of Montreal, when they 
Were described as being gneissoid in structure, and as inter- 
Stratified with true gneisses and with crystalline limestones. 
In 1854, the writer, in concert with Logan, proposed for the 
ancient crystalline rocks of the Laurentide Mountains, includ- 
ing the lower and upper gneissic groups already mentioned, 
and the succeeding labradoritic rocks (but excluding the chlo- 
Nitic and greenstone series), the name of Laurentian, In an 
h 
greenstone series, which had been shown to overlie unconform- 
ably the Laurentian in Canada. 
Studies of Credner, of Brooks and Pumpelly, and of Irving, 
have, however, all confirmed the views of the Canadian survey 
