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of geological time, is one of the clearest proofs we can have of a 

 progressive elevation in the scale of structure of the races suc- 

 cessively created. The law of successive appearance of the foot- 

 prints, is quite as conclusive as that of the parallel introduction 

 of the actual skeletons and remains of the creatures themselves ; 

 it is perhaps of even more weight, as precluding all discussion 

 upon the differences in degree of deslructibility of the bones or 

 carcases of the several classes of animals which peopled the 

 ancient world. Some of the bird-tracks and reptilian footprints 

 left on the once soft surfaces of the old rocks, are as clear and 

 legible imprints as any impressed yesterday on surfaces of moist 

 mud or sand, by the creatures of corresponding structure. Once 

 buried and sealed up, their preservation has been independent 

 of the lapse of time. This law of a progressive rise in the 

 character of the footprints, like that so generally recognized in 

 regard to the organic remains themselves, distinctly refutes the 

 view urged by Sir Charles Lyell, and some other disciples of 

 the Huttonian theory of the earth's history. Fancying a uni- 

 formity in the series of past changes in the animate and inani- 

 mate world, they contend that the evidence in support of the 

 theory of the progressive development of organic life is incon- 

 clusive, on the ground that the higher forms being inhabitants of 

 the land, we ought not to look for their remains in strata of marine 

 or aqueous origin, but must suppose they were never entombed. 

 But the negative evidence from footprints is of positive force, 

 when it appeals to appearances in the imprinted surfaces of the 

 rocks, which show that they were exposed in a moist state to the 

 air, above the level of the waters, and in situations as accessible 

 to mammalia as to birds, and in the case of the still earlier for- 

 mations, as accessible to both mammalia and birds as to the rep- 

 tiles, which left their tracks in such numbers upon them. 



Prof. H. D. Eogers also adverted to the superior value of the 

 evidence afforded by such unequivocal shore marks as those of 

 the footprints, and the markings which usually accompany them, 

 over that of the " ripple markings," so generally appealed to by 

 geologists as the signs of the ancient water levels or sea margins 

 of the globe. Explaining, in accordance with the suggestions of 

 Babbage, how these latter may be produced under deep water, 



