372 
but the specimens which belonged to the latter, consisting of 
fossils found in this locality, had been removed to Leeds, 
and now formed part of the collection of the Philosophical 
Society in that town. The Chairman concluded by ex- 
pressing a hope that the Society would meet with more 
encouragement than it had hitherto done. 
H. C. Sorb y, Esq., F. G. S., of Sheffield, then read a Paper — 
ON THE MOTIONS OF WAVES, AS ILLUSTRATING THE STRUC- 
TURE AND FORMATION OF STRATIFIED ROCKS. 
For some years past I have paid much attention to the 
effects of currents during the formation of stratified rocks, 
and to the determining of their directions in numerous 
places. Though I have now accumulated very many facts 
connected with this subject, yet hitherto I have not felt 
justified in publishing them, on account of there still remain- 
ing many points difficult to decide to my entire satisfaction ; 
and though I now purpose to give an outline of my present 
views, yet still I consider it very probable that they will have 
to undergo considerable modification. So far as I have at 
present determined, there were two apparently distinct kinds 
of currents present during the formation of most stratified 
rocks : one produced by tidal or surface waves, character- 
ised by moving backwards and forwards along a particular 
line ; and the other flowing only in one direction, the origin 
of which I have not yet entirely ascertained, and probably 
due to different causes under different conditions. I might, 
however, remark, that in the coal strata near Sheffield, where 
this structure is seen in great perfection, I am of opinion 
that it indicates currents affecting a tideless sea, not commu- 
nicating with the main ocean by a wide opening. In the 
lower part of the millstone grit there is evidence of oscilla- 
tion, as if the tide had a slight access ; which, however, does 
not appear to have been the case with the lower part of the 
