POOUTPRINTS 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 
—hirds, 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 
