of Corn Cockle Muir. 145 



separating two layers, were it not for the friable nature of the 

 sandstone, which causes it to break and remain in the matrix, 

 as it were, the lower surface of an upper layer would exhibit 

 an exact cast of the indentation beneath. As it is, the sub- 

 stance of the sandstone thus remaining in adheres so slightly 

 to the cavity, that it is generally easy to scrape it out, without 

 at all injuring the shape of the foot-mark. This fact will de- 

 cidedly prove that the marks do not proceed from any fossil 

 contained in the sandstone (an idea which might probably 

 occur to a person who had not seen any specimens) ; as, in 

 that case, an indentation would be left both in the upper 

 and under laminas, which is not the case. 



The strongest proof that the marks were caused by animals 

 is their arrangement in two parallel lines, and at regular dis- 

 tances from each other, and the agreement in shape and 

 position of the alternate marks, by which the hind foot is 

 easily distinguishable from the fore. One specimen, a slab 

 about 8 ft. long, which was taken out of the quarry some years 

 ago, contains no less than twenty-four footsteps, in which the 

 most perfect order is preserved ; so that, were it not for the 

 hardness of the stone, it would not be difficult to believe that 

 an animal had just passed over it. 



In this specimen the mark of the hind foot comes up to, 

 and in some places partly effaces that of the fore. In the 

 quarry the footsteps are found ranging in distinct and regular 

 tracks. Their direction is up and down the strata ; in no 

 instance do they extend across. They are not all of the 

 same size or shape. In one set the toes in the front of the 

 foot have left a very distinct impression, while the heel has 

 displaced and turned up the sand behind at each successive 

 step. In another variety the toes are scarcely discernible, and 

 the heel seems to have slid some way from the spot where it 

 was first put down, gradually sinking until the animal acquired 

 a firm footing. The difference of these two sets of marks has 

 been accounted for by supposing them to have been caused, 

 the former in the ascent, the latter in the descent, of the ani- 

 mal. If that were the case, we must suppose that the sand- 

 stone existed in its present inclined position while yet in a soft 

 state; a fact quite at variance with the theories at present 

 current among geologists. 



The cause of this difference may perhaps be explained by 

 supposing that they are the foot-marks of distinct species of 

 animals. As they are never found intermixed, but always in 

 separate tracks, and as, in the latter of the two varieties 

 enumerated, the length of the steps is greater than in the 



Vol. I. — No. 2. l 



