the Mode of Deposition of the Coal Strata. 247 



ble objections, which must occur to the mind of every one who 

 is adequate to the consideration of the present circumstances 

 of inland lakes, even in the most thickly-wooded countries. 

 But without dwelling upon these objections, I shall proceed 

 to notice two facts which have but lately been brought to 

 light, and which appear to me to be of the most conclusive 

 nature, and utterly destructive of this long- received theory. 



The first of these facts is the very recent discovery of ex- 

 tensive strata in the coal-fields, containing sea shells in great 

 abundance, of which an interesting account has already ap- 

 peared in your pages from the pen of Mr. J. Phillips, in your 

 Number for November 1832. Nor are these marine strata 

 so situated with respect to the beds of coal as to leave the 

 smallest doubt of their having been actually deposited by the 

 sea. They are found to extend over a very wide district, and it 

 cannot therefore be for a moment supposed, that the sea-shells 

 were, in a manner, accidentally introduced amongst what have 

 hitherto been looked upon as fresh- water deposits. I have 

 lately had presented to me specimens of sea- shells from a bed 

 of coal shale near Wigan, in Lancashire; and as this locality 

 is situated on the western margin of the same great coal-field 

 which has been so ably traced by Mr. J. Phillips, as having 

 an intermixture of marine strata, it appears probable that the 

 specimens now in my possession have been derived from a 

 continuation of the same beds; although I have not yet ascer- 

 tained the particular situation in which they were found. 

 These shells are bivalve, of about two inches in diameter, are 

 much injured by pressure, but may still be distinctly defined. 

 They appear to me to resemble most nearly the genus Mac- 

 tra, and especially the M. Lutraria of Wood's Catalogue. 

 So singular and conclusive a fact, although similar instances 

 have not yet been brought to light in any great variety of 

 cases, not only affects most materially the very foundation of 

 the lacustrine theory, but even brings at least one portion of 

 the coal strata distinctly within the catalogue of marine de- 

 posits; and when we consider that the existence of these ma- 

 rine strata has only lately become known, not in a new series 

 of coal mines, but in a district supposed to be perfectly well 

 known to geologists, we cannot but anticipate a speedy in- 

 crease to our store of similar facts, as the lights of science 

 begin to shed a more steady lustre on those who are most 

 intimately connected with the coal districts. 



The second class of facts to which I before alluded, have 

 even a stronger bearing upon the manner of the coal deposits 

 than these marine strata have upon their general character. 

 I mean the existence of large entire trees, in various parts of 



