310 Dr Duncan 07i Foot-7narks of Animals, t^-e, 



pressions which animals might have made at low water, by 

 moving over the surface of the sands they were depositing. 



In the midst of so much difficulty, it is not easy to form 

 ■even a plausible conjecture as to the manner in which the 

 sand composing ihe rock was originally accumulated. It 

 might, however, be perhaps worth while to inquire whether 

 or not this successive accumulation could be the effect of the 

 drifting occasioned by violent winds from the south-west. 

 Supposing a sand-hill to be thus formed, a period of r^iiny 

 weather following the stormy season would soften and diffuse 

 the particles of clay, which may easily be believed to have 

 mingled with the sand-drift, and would not only prevent the 

 sand from being again moved by the wind, but would form it 

 into a substance of some tenacity, resembling mortar, well 

 fitted for preserving any impression which it might receive. 

 If, during or immediately after the rainy season, animals were 

 to traverse a hill thus formed, their tracks would be either al- 

 together obliterated, or partially filled up, of which latter 

 state many traces are to be found in the quarry ; but when 

 the surface had begun to dry, the foot-marks impressed on it 

 would remain a considerable time quite distinct and well de- 

 fined. Now, supposing the stormy monsoon again to com- 

 mence, the neighbouring sands, which had not yet been fixed 

 by any mixture of clay, and which happened, from their situ- 

 ation, to be easily dried by a few days of favourable weather, 

 would be suddenly drifted on the hill in question, forming a 

 layer which may easily have covered over the half-indurated 

 surface, without being incorporated with it, and without ii^ 

 any way injuring the form of the footsteps imprinted on it. 

 Let the monsoon be now supposed to continue during the 

 whole course of a dry summer : Fresh layers of sand would 

 be drifted, pure at first, but mingled again towards the close 

 of the season with the clayey dust swept from an arid soil, 

 which mixture would form the materials of what the quarry- 

 men know in its present state by the name of a day-face, and 

 would once more, when subjected to the operation of the re- 

 turning period of rain, both fix the sand, and prepare it for 

 the reception of permanent impressions of the tracks of wan- 

 dering animals. Thus from year to year the same round 



