DELICATE FOSSIL MARKS. 255 



another set of circumstances, may endure for indefinite 

 periods of time : as for instance where the action 

 of the elements happens to spare certain spots of ground, 

 leaving the marks made upon them undisturbed ; in 

 such a case mere lapse of time may fail to effect their 

 erfacement. 



It is true that in reviewing the existence of excep- 

 tional cases of this nature, we travel somewhat outside 

 the ordinary bounds of the tracksman's craft; yet all 

 such matters are well worthy of the intelligent hunter's 

 consideration, as examples of how slight traces of man 

 or animals may under certain conditions survive the 

 accidents of time. 



These conditions may assume very great and unex- 

 pected varieties of form, and human ingenuity may be 

 taxed to its utmost, even to suggest an explanation as 

 to the origin of some of them ; take for instance the 

 fossil tracks, left embedded in the rocks, which furnish 

 us with proof positive of how even the most delicate 

 markings upon the ground may be perpetuated and 

 preserved for ever. These consist of ripples made by 

 the tides upon the primeval sands; and also examples 

 of the actual footprints left by extinct mammalia, birds, 

 and reptiles, and even insects, now become hardened 

 into stone. Such things may be seen exhibited in most 

 of our leading museums. 



There is also the far larger but no less wonderful 

 class of the impressions left- upon the ancient mud 

 by leaves of trees or of ferns, and other delicate growths 

 of vegetable origin, which are found in enormous 

 quantities, and in the most perfect state of preserva- 

 tion, in many countries, and in many different kinds 

 of rock. 



