144 INTRODUCTION. 



causes through a period of mdefinite duration, might 

 have produced even a more general diffusion, but, as an 

 impenetrable veil hangs over everything that preceded 

 the historical epoch, and we know of no facts which cor- 

 roborate this latter suggestion, we cannot place much 

 rehance upon it. We must seek then for other causes, 

 to explain the general dispersion of this and other cos- 

 mopolite species.^ 



Of the origin and mode of creation of organized 

 beings, we of course can know nothing, through our own 

 limited faculties. The subject is beyond our comprehen- 

 sion, and Divine Providence has vouchsafed to us no 

 revelation concerning it. The Mosaic account of cre- 

 ation informs us that after the surface of the earth was 

 prepared for the support of animal life, the different 

 classes of animals were created at different periods of 

 time, and our own experience, drawn from observation 

 of the fossil remauis of former animals, which have been 

 preserved in the strata of the earth's crust, fully cor- 

 roborate this account. But, we are limited to these 

 very general facts, and must found our views of the 

 local origin, and the subsequent dispersion of species 

 over the earth upon such observations as we possess, and 

 such reasonings as we can base upon them. 



1 A similar course of remark might be pursued in relation to Bulimus 

 lubricus, and Vitrina pellucida, the former abundant and generally diflused 

 in the country, the latter rare and found only in insulated situations, but in 

 every case directly upon the route followed by hunters and fur-trappers, 

 from the earliest seltleineiils. 



