GEOLOGY. 333 



local. Over the wider field of life, at any given epoch, the change has been 

 gradual; and, as it would seem, obedient to some general, but as yet ill- 

 comprehended law. In regard to animal life, and its assigned work on this 

 planet, there has, however, plainly been an ascent and progress in the main. 



Although the Mammalia, in regard to the plenary development of the 

 characteristic orders, belong to the Tertiary division of geological time, just 

 as "Echini are most common in the superior strata; Ammonites in those 

 beneath, and Product! with numerous Encrini, in the lowest " of the 

 secondary strata; yet the beginnings of the class manifest themselves in the 

 formations of the earlier preceding division of geological time. Xo one, 

 save a prepossessed Uniformitarian, would infer from the Lucina of the 

 pcrmian, and the Opis of the trias, that the Lamellibranchiate Molluscs ex- 

 isted in the same rich variety of development at these periods, as during 

 the tertiary and present times; and no prepossession can close the eyes to 

 the fact that the Lamellibranchiate have superseded the Palliobranchiate 

 bivalves. 



On negative evidence, Orthisina, Theca, Producta, or Spirifer, are be- 

 lieved not to exist in the present seas : neither are the existing genera of 

 siphonated bivalves and univalves deemed to have abounded in pcrmian, 

 tnassic, or oolitic times. To suspect that they may have then existed, but 

 have hitherto escaped observation, because certain Lamellibranchs with an 

 open mantle, and some holostomatous and asiphonate Gastropods, have 

 left their remains in secondary strata, is not more reasonable, as it seems to 

 me, than to conclude that the proportion of mammalian life may have been 

 as great in secondary as in tertiary strata, because a few small forms of the 

 lowest orders have made their appearance in triassic and oolitic beds. 



Turning from a retrospect into past time to the prospect of time to come, 

 - and I have received more than one inquiry into the amount of prophetic 

 insight imparted by Palaeontology, I may crave indulgence for a few 

 words, of more sound, perhaps, than significance. But the reflective mind 

 cannot evade or resist the tendency to speculate on the future course and 

 ultimate fate of vital phenomena in this planet. There seems to have been a 

 time when life was not; there may, therefore, be a period when it will cease 

 to be. Our most soaring speculations still show a kinship to our nature; 

 we see the element of finality in so much that we have cognizance of, that 

 it must needs mingle with our thoughts, and bias our conclusions on many 

 things. The end of the world has been presented to man's mind under 

 divers aspects : as a general conflagration : as the same, preceded by a 

 millennial exaltation of the world to a Paradisiacal state, the abode of a 

 higher and blessed race of intelligences. If the guide-post of Palaeontology 

 may seem to point to a course ascending to the condition of the latter 

 speculation, it points but a very short way; and, in leaving it, we find our- 

 selves in a wilderness of conjecture, where to try to advance is to find our- 

 selves "in wandering mazes lost." 



With much more satisfaction do I return to the legitimate deductions 

 from the phenomena we have had under review. 



In the survey which I have taken, in the pi-esent course of lectures, of the 

 genesis, succession, geographical distribution,, affinities, and osteology of 

 the mammalian class, if I have succeeded in demonstrating the perfect 

 adaptation of each varying form to the exigencies and habits and well- 

 being of the species, I have fulfilled one object which I had in view, viz., to 

 set forth the beneficence and intelligence of the Creative Power. If I have 



