FOOTPRINTS ON THE SANDS OF TIME 29 



enabling us in imagination to see them as they were when they 

 walked this earth. It will be our endeavour in the present work 

 to present to our readers a certain number of these antique animals 

 birds, beasts, and fishes, whose mortal remains have been buried 

 up and preserved, often with singular completeness, in the rocks 

 of the earth's crust. 



But although fossil bones and skeletons are the chief material 

 at our command for this purpose, yet the series of stratified rocks 

 contains here and there other kinds of evidence, valuable in their 

 way, such as footmarks, tracks, burrows, coprolites, or droppings, 

 and even ripple-marks and the impressions of rain-drops. It is 

 with these evidences that we propose to deal in the present 

 chapter. Let us see what can be learned from such humble and 

 apparently insignificant records, of some of the creatures that 

 once trod this earth. 



The intelligent observer who has strolled along the strand of 

 the seashore at low water, must have often seen the surface of 

 the exposed sands deeply rippled by the waves of the ebbing tide, 

 and have noticed the trails of molluscs, and the meandering 

 furrows and ridges produced by worms, or annelides, and the 

 tracks of crabs, and sometimes the footprints of birds and of dogs 

 or other quadrupeds that have walked over sand or mud while 

 it was yet plastic and sufficiently firm to retain the markings 

 impressed upon it. Under certain conditions these apparently 

 evanescent characters are indelibly fixed on the stratum, and in 

 rocks of immense antiquity successive layers of sandstone and 

 shale, through a thickness of many hundred feet, are found deeply 

 furrowed with the ripples of the waves that flowed over them, 

 pitted by the rain that has fallen upon them, and impressed with 

 the footmarks of bipeds and quadrupeds that traversed the sands 

 whilst the surface was in a moist and yielding state. Even on 



