260 Dr Hibbert on the Limestone of Burdiehouse, 



which greatly overtop the lacustrine deposits we have been con- 

 templating. 



The uppermost strata of the coal-measures of Loanhead, 

 comprise alternating beds of sandstone, argillaceous and bitumi- 

 nous shale, along with ironstone bands, coal, and some little lime- 

 stone ; the workable beds of coal, two to ten feet in thickness, be- 

 ing about twenty-five in number. 



By these beds numerous oscillatory movements are made 

 known to us. Some of the alternations of sandstone, and argillace- 

 ous shale, might have been induced by matter drifting from dif- 

 ferent localities ; and, of course, varying with such localities. 

 But, in other instances, particularly where we find strata alter- 

 nating with coal, we must refer the whole to corresponding oscilla- 

 tions of the earth's surface, by which a land covered with ferns 

 and other plants has been submerged beneath a fresh- water lake, 

 only to reappear ; — and only to be succeeded by other alternate 

 submersions and emersions, incidental to the early history of our 

 planet. 



SECTION X.— THE EFFECTS OF OSCILLATORY MOVEMENTS OF THE EARTH'S 

 SURFACE, CONSIDERED IN REFERENCE TO THE ANCIENT VEGETATION AND 

 ANIMALS DESCRIBED IN THE PRESENT MEMOIR. 



That these oscillatory movements of the earth's surface must 

 have caused corresponding changes in both vegetable and ani- 

 mal life may be expected. M. Adolphe Brongniart has fre- 

 quently made observations on the differences of such plants as 

 occur in the lower and upper beds of the carboniferous group. 

 And, in the present instance, the Sphenopteris affinis and some 

 few other ferns are, I suspect, confined to the inferior strata of 

 the Lothian coal-fields. 



With regard to the races of animals which inhabit waters, 

 corresponding changes have been noticed. M. Agassiz has re- 

 marked, that, in a suite of strata belonging to any given forma- 

 tion, he has found few fish in a lower bed to agree as a whole 



