308 Dr Duncan 07i Foot-marks of Animals 



fessor Buckland, with whom I have been in correspondence, 

 having favoured me with his opinion on the subject. That 

 eminent individual, supposing the sandstone to have been de- 

 posited at an era when, according to the received opinion, no 

 animals existed on our earth of a higher order than reptiles, 

 was induced to look to our present crocodiles or tortoises as 

 the species most nearly resembling those of whose footsteps I 

 sent him casts; and on making experiments with some live 

 tortoises which he has in his possession, he has come to the 

 conclusion, that to animals of this species the tracts belong. 

 With regard to the sliding impressions in particular, he says 

 that he fully adopts my theory of their origin, his tortoises, in 

 going down a declivity over wet sand, having made " almost 

 exactly the same impressions." 



There are some curious facts connected with this phenomenon 

 which have not yet been mentioned, and which the limits I 

 must prescribe to myself will not allow me to do more than 

 enumerate:-^ 



1^^, In most instances the counter impressions are distinctly 

 marked in relief on the under surface of the layer covering the 

 foot-prints, these projections corresponding to the cavities be- 

 low as exactly as a cast to its mould. 



2c?, The impressions never occur but on what the workmen 

 call a clay face, by which is meant a stratum, the outer coat of 

 which has a slight admixture of clay, rendering it harder than 

 the rest of the rock, accompanied sometimes with a thin layer 

 of soft clay in the seam between the under and upper stratum. 



3(i, All the tracks are constantly in a direction either up or 

 down, sometimes inclining a very little either to the right or 

 left, but never running across the slope in any great degree. 



4i7i, In most of the impressions there are marks of the mat- 

 ter being displaced by the foot-marks, and wherever such an 

 appearance occurs, the matter is found to have been carried 

 directly downwards, with reference to the present inclination 

 of the quarry. 



These two last circumstances, as well as that of the sliding 

 tracts, prove that the strata must have been very much in- 

 clined, while in a soft state, and while in the act of forming. 



