

 PREFACE. 



' 

 THE subject which I have undertaken to bring before the 



consideration of the scientific reader is one of acknowledged 

 importance, and requires, to do it justice, the exertion of talent, 

 time, and application, beyond my humble pretension. I there- 

 fore wisli it had fallen to more efficient hands to bring it 

 forward, with the requisite advantages due to the merits of 

 such a discussion. 



There is a cautious negative system of tactics in strong 

 alliance with our present School of Philosophy, valuable as to 

 the preservation of our views within the bounds of well-defined 

 and "pace-worn" paths, macadamised, with a host of stubborn 

 incontrovertible facts, which guide the erratic investigator, and 

 prevent his soaring above their horizon, and perchance losing his 

 way in the inviting mazes of speculative inquiry and this is so 

 far beneficial; but its disadvantages are equally obvious from 

 its powers of restriction and contraction, which keep enchained 

 the inspiring spirit of investigation, from which, in the bare 

 collision of adverse opinion, some new facts of benefit to science 

 may be derived. 



If, on the other hand, we rest satisfied with the limits of our 

 meandering ways on the verge of an immense circle, to the 

 centre of which we are only to approach by parallels as formal 



