AlfinVEESAEY ADDEESS OF THE PEESIDEXT. 85 



have hesitated to refer all these to the former series, and cannot say 

 from the specimens where the line of division comes, although one 

 of the so-called Huronians is less coarsely crystalline than the 

 admittedly Laurentian. The difference, however, is not greater than 

 might be readily explained by a bringing together by faulting of 

 rocks originally some distance apart in the same series ; and, as all 

 the specimens give indications of a very ancient crushing, it is quite 

 possible that this may account for the apparent diversity, which is 

 after all hardly greater than we may observe in some cases of con- 

 secutive masses near Gairloch. I may add that, Avhen at "Winnipeg, 

 I saw in the Museum some specimens of the Huronian and Lauren- 

 tian from the same region, and did not see how the former were to 

 be separated from the latter. 



A collection of slides also of Huronian rocks from the south of 

 Lake Superior, selected by Dr. A. AYichmann, has been lent to me 

 by Prof. Judd. Several of these remind me of specimens which I 

 obtained to the east of that lake. Some are distinctly of clastic 

 origin, containing small fragments of Laurentian gneisses, but with 

 considerable alteration in the matrix ; others have a general resem- 

 blance to members of the uppermost group of Alpine schists, while 

 others, again, seem hardly more altered than a Cambrian slate, when 

 it has been subjected to rather exceptional pressure. Some of the 

 slides are obviously from rocks of igneous origin, and so cannot be 

 taken into consideration. The first named of these specimens indi- 

 cate that the break between these and the Laurentians must be 

 considerable. 



When in Canada, I saw specimens of the red felstones correlated 

 by Dr. Sterry Hunt with the Arvonian of Dr. Hicks. They 

 undoubtedly bear, macroscopically, a close lithological resemblance 

 to the devitrified rhyoHtes of the Bangor-Carnarvon district. 



I was not able to visit any exposure of rocks placed in the Mont- 

 alban group. The specimens shown to me by Dr. Sterry Hunt bore a 

 remarkable resemblance to members of the Tremola schists and the 

 underlying gneisses of the Lepontine Alps. I did not visit any area 

 occupied by the rocks called Taconic, and so have not been able to 

 form any opinion as to the value of the group. 



With regard to the stratigraphical sequence of these groups, it 

 would be presumptuous in me to express a very decided opinion. 

 But I will venture to say that, if the red felstone (petrosilex) group 

 underlies the Montalban series (except by intrusion), it will be the 

 most startling and inexplicable fact that has come to my knowledge 

 since I began to work at this branch of petrology ; and that while 

 it is very probable that some of the rocks now assigned to the Huro- 

 nian may immediately follow the Laurentian or in some cases be a 

 part of it, others, I think, must be decidedly later than the Montalban ; 

 if not, the teaching of nature in the New World contradicts the 

 lessons which she gives us in the Old World. 



Cornwall and South Devon. 



As I have already described, in the pages of our ' Journal," the 

 VOL. xLn. h 



