in the Neighbourhood of Edinburgh. 275 



an included band of' limestone, similar in mineral aspect to the lacustrine limestones 

 of central France, and containing minute shells, referable to fresh- water genera.'' ,, 



Mr Murchison has publicly pointed out to me this passage, which, from my 

 residence abroad, I had not seen, but which I am sure, if I had read, would have 

 escaped my recollection, from its apparently trivial importance. 



The reply which I have to make is, that if my discovery of extensive beds of la- 

 custrine limestone is to be superseded by mere bands of fresh-water limestone, Mr 

 Murchison himself has been anticipated by other writers. The Rev. Mr Ure, in 

 his History of Rutherglen, written at least forty years ago, states, in reference to 

 certain fresh- water muscles, or unios, enclosed in a band of limestone, that " the shells 

 were commonly entire, and were 'probably produced in fresh water." — History of 

 Rutherglen and Kilbride, p. 311. 



Granting, however, that Mr Murchison 1 s limestone is thicker than what is 

 usually meant by a band of limestone, the various limestones which I have enume- 

 rated are not, like his, contained within beds of coal, but, on the contrary, form con- 

 siderable deposits beneath beds of coal. This difference has been remarked by Mr 

 De la Beche. — Geological Researches, p. 319. 



But waving these very subordinate considerations, I shall state in my own defence, 

 that my memoir was drawn up at a time when many British geologists were inclined 

 to admit, with a writer of the first weight, that no instance had yet been discovered 

 of a pure lacustrine formation of the carboniferous era ; and that although there 

 were some instances of shells, apparently fresh water, which might have been washed 

 in by small streams, they did not by any means imply a considerable extent of dry 

 land. (See Ly ell's Principles of Geology, 1st Ed. vol. i. p. 130, and vol. iii. p. 15.) 



My own discovery, however, of the fresh- water character of the limestone of Bur- 

 diehouse, in conjunction with that of other similar limestones of still greater thick- 

 ness and extent, viz. at Calder and elsewhere (See the Supplement to this memoir), 

 have, I trust, tended to set geologists right upon the question of pure lacustrine de- 

 posits existing during the carboniferous epoch. 



But after all, — these disputed claims of originality may neither belong to myself 

 nor to any other British geologist. The far older speculations of M. Deluc and of 

 M. Alexandre Brongniart, refer all the varieties of strata comprehended in coal- 

 measures to a lacustrine origin ; while their theory upon the alternation of these 

 strata with marine deposits has, in some few respects, coincided with the principles 

 which I have sought to establish in the present memoir. — (Tableau des Terrains, 

 par Brongniart, p. 280, &c.) 



With a third charge I was industriously assailed during the meeting of the Bri- 

 tish Association of Science at Edinburgh. It was contended that I had given an er- 

 roneous position to the limestone. My present memoir will however show, that the 

 view which I originally entertained on this question remains unaltered. I went over 

 the ground with some of our most distinguished geologists, among whom was Dr 



m m 2 



