Proceedings of the Society. 183 
The Silurian, Devonian, and Carboniferous were then treated of 
and detailed evidence shown as to their conformity to the types of 
Western Europe rather than to those of America. 
In conclusion, it was pointed out that though the great systems 
of formations can be recognized throughout the Northern Hemi- 
sphere, their divisions must differ in the maritime and inland 
regions, and that hard and fast lines should not be drawn at the 
confines of systems, nor widely different formations of the same age 
reduced to an arbitrary uniformity of classification not sanctioned 
by nature. It was also inferred that the evidence pointed to a per- 
manent continuance of the Atlantic basin, though with great 
changes of its boundaries, and to a remarkable parallelism of the 
formations deposited on its eastern and western sides. 
DISCUSSION. 
The PrusmDEnt, whilst recognizing the importance of the paper, 
doubted whether the question of correlation of the Pre-Cambrian 
rocks on either side of the Atlantic was ripe for discussion. 
Dr. Hicks felt sure that the paper would be welcomed on this 
side of the Atlantic. He agreed with most of the conclusions of 
the Author, including the correlation of the Huronian with the 
Pebidian. This was borne out, not only by similarity of lithological 
characters, but by the exact correspondence of the succeeding beds 
in the two areas as shown by Mr. G. F. Matthew. The difficulty 
of correlation lay with the rocks below the Huronian. He noticed 
that fragments of granitoid rocks occurred in the Huronian as in 
the Pebidian. He had also called attention to the contrast between 
the Palzeozoic rocks of the ocean borders and those of the interior 
of the continents, in papers read before the Society and elsewhere. 
Dr. Scorr referred to Mr. Walcott’s work, and mentioned the 
occurrence of great deposits of Pre-Cambrian rock in Arizona. 
Where terrestrial species play an important part, difficulties of 
correlation were much increased. 
Dr. Hiypn noticed the difference between the coast-geology of 
America and that of the interior. 
Mr. Mare stated that the paper referred very fully to the point 
noticed by the last speaker. 
