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170 



€ EOLOG Y- 



[Sect. VI. 



these islands had once been united to Europe, thus en- 

 larging wonderfully our ideas of the ancient geography 



of the Atlantic : so also the remains of a mastodon are 

 said to hare been brought from Timor, thus perhaps 

 indicating the road by which this great quadruned 



formerly reached Australia. 



Fossil Footstep 

 footsteps may be 



As allied to organic remains, fossil 

 here referred to. They have been 

 observed in Euro}>e and North America, but hitherto in 

 no other part of the world. These curious vestiges not 

 only proclaim the former existence of reptiles and birds 

 at very remote periods, and in rocks often not containing 

 a fragment of bone, but they generally prove that the 

 level of the land subsided after the animal had left its 



impress on the ancient sea-beach, thus allowing thousands 

 of feet of strata to be thrown down over them. The 

 best place for searching for footsteps is in quarries of 

 sandstone^ in which the strata are separated by seams of 



shale. The best indicati 



jn of their probable occurrence 

 is the rock being ^^ rippled,'' that is marked with narrow 

 little wavy ridges, such as occur on most sandy shores 



when 



the tide 



is down, and wliich indicate that tlie now 



--■^ 



rocky surface w^as once either a tidal beach or a shall 

 surface, over ¥/hich the ancient animals w^alked. In the 

 case of fossil footsteps being found, the largest slab 

 which could possibly be removed ought to be br aight 

 away, and accurate drawings, or still better, casts, mad^ 

 of several of the footsteps. A plan from accurate mea- 

 surement ought to be taken of any row of steps. The 

 value of such fossil footsteps would be in a manifold 

 degree increa^-^d, if the age of the deposit cor^'^ be 



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