MS Prof. Sedgwick on the May Hill Sandstone, 



formable to^ and appears to pass into, the coal-measures. About 

 the commencement of the Triassic period, these Permian sand- 

 stones underwent contortions along with the coal strata; in 

 consequence of which we see, in Warwickshire, the upper triassic 

 groups resting discordantly upon the inclined beds of the sand- 

 stones. 



In conclusion we may remark, — 



1. That it is not in all cases an easy matter to draw a clear 

 line between this series and the Carboniferous. Thus Mr. W. 

 Smith, in his old geological map of Yorkshire, considers the 

 lowest group (No. 5) as one of the coal-measures. The series 

 most frequently commences with a discordancy of position and 

 a coordinate change of organic types. With limited exceptions, 

 the flora and fauna of the Permian groups differ from those of 

 the carboniferous period. 



2. The several groups of the series admit of very close com- 

 parison with the Rothe-todte-liegende, the Kupfer Schiefer, and 

 the Zechstein, &c. of Germany. 



As a general conclusion to the preceding tabular view, we may 

 remark, that in the vast succession of the palaeozoic rocks there 

 is a difficulty in drawing a well-defined line between the several 

 subdivisions — Cambrian, Silurian, Devonian, Carboniferous, and 

 Permian. But that difficulty is no reason for confounding any 

 two of the subdivisions under one name. To do so would be to 

 conceal a difficulty, not to solve it. There ought now to be no 

 difficulty in the separation of the Cambrian and Silurian groups ; 

 for a clear line has been drawn between them. But there is as 

 yet an unsolved difficulty in drawing a line between the true 

 Silurian and the Devonian groups; and there yet remains a 

 doubt as to the exact line of separation between certain Devonian 

 and carboniferous rocks, as well as between some carboniferous 

 beds and the base of the Permian series. 



Conclusion. 



Returning to the Lower Palaeozoic divisions. On what 

 grounds, it may be asked, have I endeavoured to fix their geo- 

 graphical nomenclature? On the same grounds (I reply) on 

 which the Silurian and Tertiary nomenclature (and that of all 

 other secure parts of the whole English series) have been fixed — 

 namely, by determining by hard field-labour the real succes- 

 sion of physical groups ; and then completing them, and some- 

 times correcting their boundaries, by the help of their organic 

 contents. I affirm, with perfect confidence, that the Cambrian 

 series is rightly named, because its successive subordinate parts 

 have been established on that double system of physical and 

 fossil evidence to which I have before alluded. The nomen- 



