AT STOURTON HILL. 45 



acquires very different properties where it has been subjected 

 to pressure from superincumbent strata, and to greater heat 

 from volcanic action; as around Edinburgh, where it has been 

 consolidated by the volcanic agency, which has thrown up 

 Arthur's seat, Salisbury Crag, the Calton-hill, Castle-hill, 

 Inchkeith, and other masses of trap rocks, — and where this 

 sandstone forms the beautiful material of which that city is 

 built. In Stourton quarry there are two distinct strata of 

 these footmarks, about two feet vertically separated from each 

 other, and the workmen believe that there is a third stratum 

 of the same impressions a very little lower in the rock ; but I 

 have been able to examine only the two upper strata of these 

 remarkable impressions. This specimen, and the others in 

 Liverpool, were obtained from the upper stratum of markings, 

 which occurs at a vertical depth of 37 ft. from the actual sur- 

 face of the rock. The lower stratum of footmarks is 39 feet 

 from the surface of the rock, and the sandstone in this quarry 

 has been worked in some places to a depth of nearly 100 ft. 

 and has been pierced for a well to a further extent of 40 ft. 

 without reaching the lower limit of this bed of new red sand- 

 stone. The continuity of this bed of sandstone is only inter- 

 rupted by occasional very thin conformable layers of soft clay, 

 which vary from one line to two inches in thickness. The 

 prints of the feet have always been first made on the upper 

 surface of these thin layers of clay, which have but imper- 

 fectly communicated them to the surface of the rock below, 

 but have given most perfect casts of these impressions to the 

 under surface of the superincumbent rock. The specimen 

 before you, therefore, and all the others which have been ob- 

 tained, do not represent the prints left by the animal on the 

 soft substance on which it once trod, but are perfect casts of 

 these prints taken by the under surface of the rock immedi- 

 ately above. The same is the case with the foot impressions 

 met with in Scotland, Germany, America, and everywhere 

 else, indeed, the impressions could not have been preserved 

 but by the intervention of this clay, which, by interrupting 

 the continuity of the sand-deposits, has prevented these prints 

 from becoming obliterated. There are also innumerable 

 small isolated pieces of soft clay spread through the texture 

 of the sandstone, and the superincumbent soft clay is much 

 used in this neighbourhood in brick-making for building. — 

 A large portion of the present floor of Stourton quarry exhi- 

 bits the inferior stratum of foot impressions, at the depth of 

 39 ft. from the surface of the rock ; but as the clay which re- 

 ceived the prints adheres tenaciously to the under surface of 

 the superincumbent rock, which has been there removed, the 



