312 FOSSIL FOOT-PRINTS [CHAP. XXXVII. 



found both above and below the level of the reptilian 

 foot-steps. 



We may safely assume that the huge reptile which 

 left these prints on the ancient sands of the coal- 

 measures was an air-breather, for its weight would 

 not have been sufficient under water to have made 

 impressions so deep and distinct. The same conclu 

 sion is also borne out by the casts of the cracks above 

 described, for they show that the clay had been ex 

 posed to the air and sun, so as to have dried and 

 shrunk. As we so often see the ripple mark pre 

 served in sandstones of all ages, and in none more 

 frequently than in the American and European coal 

 strata, we ought not to feel surprise that superficial 

 markings, such as foot-prints, which are by no means 

 more perishable or evanescent in their nature, should 

 have been faithfully preserved down to our times, 

 when once the materials had been hardened into 

 stone. 



There are some bare ledges of rock, composed of 

 pure white quartzose grit of the coal-measures, stand 

 ing out exposed above the general level of the ground, 

 in many places near Greensburg, especially near 

 Deny, in Westmoreland county, about fourteen 

 miles north of Greensburg. They are so bare that 

 scarcely any lichens grow upon them, and on some 

 of them the foot-prints of birds, as well as those of 

 dogs and some other quadrupeds have been artificially 

 cut. After examining them carefully, I entertain no 

 doubt that they were sculptured by Indians, for 

 there are many Indian graves near Derry, and one 

 of their paths, leading through the forest from the 



