﻿1851.] 



LYELL ON RAIN-PRINTS. 



243 



Fig. 2. — Rain-prints on red shale, from the New Red Sandstone or 

 Trias of Pompton, New Jersey, U. S. — W. C. RedfielcL 



these slabs, which are about half an inch thick, casts of the rain- 

 prints of a previous shower, which had evidently fallen when the 

 direction of the rain was not the same. Mr. Redfield, by carefully 

 observing the obliquity of the imprints in the Pompton quarries, as- 

 certained that most of them implied the blowing of a strong westerly 

 wind in the triassic period at that place. The form of the undu- 

 lating surface, or the ridges and furrows of the ripple, has sometimes 

 modified the depth of the impressions, which are fainter on the lee- 

 ward side of each ridge and stronger on the windward slope of the 

 same. 



One class of superficial indentations at Pompton has, I believe, 

 been correctly referred by Mr. Redfield to hail. These hail-marks 

 (see figs. 3 and 4) are deeper and much more angular and jagged in 



Figs. 3 & 4. — Supposed Hail-prints on red shale, from Pompton, 

 New Jersey. — W. C. Redfield. 

 Fig. 3. Fig. 4. 



their outline than rain-prints, and have the wall at the deepest end 

 more perpendicular, and occasionally overhanging. Fossil fish, be- 



