508 Dr. Wheelton Hind — Correlation of Carboniferous Hoclcs. 



illustrated in Mr. Gunn's scheme, and is based on the most complete 

 palEeontological and stratigraphical evidence ; and these views have 

 been published at length in the Gkologioal Magazine, Decade IV, 

 Vol. IV (1897), pp. 159, 205; Decade IV, Vol. V, p. 61. The 

 Calciferous Sandstone Series, as Mr. Gunn points out, "mainly a fresh- 

 water deposit," is probably almost unrepresented in the Midlands. 

 We know that at Thornton Force, below Ingleborough, only a very 

 few feet of conglomerate exist below the base of the Scar Lime- 

 stone ; and it is surely a normal state of things that a fresh-water 

 deposit cannot have actual homotaxial equivalents, of wide 

 extent, though, of course, marine and fresh-water beds have been 

 deposited at the same moment in different parts of an area, and may 

 therefore be said to be contemporaneous. If Mr. Gunn simply 

 means to use the term equivalents in a sense of time, of course 

 it is quite possible that, while some of the beds of the Calciferous 

 Sandstone were being laid down in the north, a deposit of limestone 

 was going on further south, just as that deposit must have been 

 going on while terrestrial conditions obtained in the north, as shown 

 by the various beds of coal. The Yoredale Series ai-e, however, the 

 real homotaxial and contemporaneous equivalents of the upper part 

 of the Carboniferous Limestone. 



The Yoredale type of rocks must have been very local, and seems 

 not to have extended very far west, for the Furness and Shap 

 districts show massive limestones of great thickness quite undivided, 

 and their southern limit appears to be about a line joining Settle with 

 Pateley Bridge, south of which the limestone is quite undivided. 



The differences in the Carboniferous succession are due entirely 

 to the conditions of deposit, land being not far away to the north 

 and north-west, so that in the Scottish area, littoral, fresh- water, 

 and terrestrial conditions obtained to a large extent, being replaced 

 by marine beds when the land sank more rapidly, while further 

 south a continuous unbroken deposit of limestone was being 

 laid down. 



In order to establish Mr. Gunn's table of equivalence, it will be 

 necessary for him to show a fauna characteristic of the Yoredale 

 Series of Phillips, and to be able to subdivide this fauna into upper 

 and lower and to trace its extension into Scotland, for up to the 

 present there is not a single fossil that can be said to be character- 

 istic of the series. It would afford some ground, too, for accurate 

 classification if it could be established that any of the limestones 

 themselves possessed a distinctive fauna; otherwise, however simple 

 it may look in a tabular scheme, the identification of any one bed in 

 a column with one in another is purely theoretical, for different 

 results would be arrived at if a datum-line were taken at the 

 top instead of at the bottom. For example, the Hardraw Scar 

 Limestone is the fifth limestone below the Millstone Grit at Ingle- 

 borough : why should it not be the fifth below the Millstone Grit at 

 Wensleydale, or in Northumberland? In fact, correlation without 

 pal^ontological evidence is absolutely of no value. 



