﻿1851.] 



LOGAN ON SILURIAN FOOT-PRINTS. 



247 



boniferous reptile*, I find not only shrinkage-cracks, but a multitude 

 of small tubercles covering a part of the surface, much resembling 

 the casts of rain-prints, and which I strongly suspect to have been 

 due to pluvial action. 



The luxuriant vegetation of the coal-period, and especially the con- 

 tinuity of its forests for hundreds of miles, as well as the botanical 

 character of its flora, had previously led botanists to infer a humid 

 climate, — still it is satisfactory to obtain positive proofs of showers 

 of rain, the drops of which resembled in their average size those 

 which now fall from the clouds. From such data we may presume 

 that the atmosphere of one of the remotest periods known in geology 

 corresponded in density with that now investing the globe, and that 

 different currents of air varied then, as now, in temperature, so as to 

 give rise by their mixture to the condensation of aqueous vapour. 

 The hail, moreover, of the triassic period, if correctly deciphered by 

 Mr. Redfield (which I see no reason to question), affords another 

 point of analogy between the meteoric agency of ancient and modern 

 times, implying that certain regions of the atmosphere were occa- 

 sionally intensely cold. 



Since the above was in type, my attention has been called to a 

 notice by Dr. Buckland, " On cavities caused by air-bubbles on the 

 surface of soft clay," which, he justly observed, " must be carefully 

 distinguished from impressions made by rainf." 



3. On the Occurrence of a Track and Foot-prints of an Animal 

 in the Potsdam Sandstone of Lower Canada. By W. E. 

 Logan, Esq., F.G.S. 



When in England, about eight years since, I exhibited to the Society 

 a specimen, brought by me from Horton, near Windsor, in Nova 

 Scotia J, which was considered to be the first faint evidence of the ex- 

 istence of reptilian animals, previous to the deposit of the Magnesian 

 Limestone. Various fossils which were brought from the same loca- 

 lity, and others from Windsor, induced Mr. Lonsdale to think that 

 the rocks were of the Triassic period, and M. De Verneuil, who had 

 just returned from Russia with Sir R. Murchison, that they were 

 Permian; but in a subsequent collection, brought by Sir Charles 

 Lyell from the same place, the same palaeontologists met with several 

 Carboniferous forms ; and Sir C. Lyell' s evidences, communicated by 

 him to the Society, left little doubt that the Horton and Windsor 

 beds were of the Carboniferous age. By a subsequent careful exa- 

 mination of the great carboniferous development at the Joggins, on 

 the Bay of Fundy, I satisfied myself that these reptilian traces oc- 

 curred near the very base of the carboniferous deposit, as the equi- 



* See Anniversary Address of the President, 1851, p. lvii. 

 f Report of Brit. Assoc. 1842, Trans. Sect. p. 57. 

 % See Proceed. Geol. Soc. vol. iii. p. 712. 



