lii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



SO moderate a distance as southern and northern England, while the 

 coal beds of the south do not contain marine admixtures for several 

 thousand feet in thickness, this is not the case when we proceed 

 northward, where we find coal beds, with deposits formerly mere 

 gravels, sands, clay and mud, intermingled with the marine animal 

 remains and calcareous strata of the carboniferous limestone period. 



There would appear little doubt, that while we take the remains of 

 animal and vegetable life entombed in rocks for our chief guides, 

 dividing off vertically, so to speak, various portions of the deposits 

 which have taken place on the surface of our planet, it is extremely 

 useful to have many divisions made in different situations for reference. 

 Thus eventually, when larger portions of the earth's surface become 

 more known than they now are as regards the distribution of land 

 and water at equal geological times, the classifications of the various 

 accumulations in vertical divisions according to the remains of animals 

 and plants found in them will be the better effected, and the com- 

 binations of physical conditions with the distribution of animal and 

 vegetable life at equal times will be the better understood. 



As far as the series of deposits in this country, known to us as 

 magnesian limestone (equivalent to the German zechstein, with its 

 associated beds), and certain inferior and perhaps superior strata, are 

 concerned, it forms part of a greater series formed under similar 

 general physical conditions, and subsequently to a very important 

 physical change effected in the same area, — a great twisting, crump- 

 ling and squeezing of previous deposits, so that part of the latter 

 were above the seas of the time and part beneath. The general 

 evidence is that the parts above water became gradually depressed 

 to a certain level, gravels, sands and mud accumulating as a whole in 

 water containing much iron, probably mechanically suspended as a 

 peroxide, the gravels forming old beaches often traceable, even up to 

 the time of the mixture of calcareous matter and mud of the lias, as 

 is well shown in Somersetshire, Gloucestershire, and South Wales. 

 Hence in our land the Permian series would become one wholly 

 founded upon palseontological considerations, inferences as to the 

 physical conditions under which it was here formed, leading us to 

 suppose it the base of deposits to the upper part of which the term 

 ' trias ' has of late years been applied. This may, however, turn out 

 to have been a mere local condition of part of western Europe, un- 

 disturbed accumulations elsewhere having been effected much more 

 generally, in which it may be as useful to make divisions as in other 

 deposits classified under the head of palaeozoic rocks, which we 

 sometimes find graduating into one another, and at other times in 

 contact in unconformable positions, according as the inferior rocks 

 may or may not have been disturbed anterior to their deposit. Much 

 has yet to be accomplished as to the history, so to speak, of the 

 rocks of this geological period, and more particularly as to the pro- 

 bable distribution of the land whence the gravels, sands and mud of 

 which they were formed have been derived. In the mean time all 

 aids towards this history are highly valuable, and hence such com- 

 munications as that of Professor Naumann are important, illustrating 



