PREFACE. 



ix 



so convinced of the soundness of the theory which 

 he advocates^ that he feels persuaded that all that is 

 needed to secure for it a ready and general accept- 

 ance, is to lay both the theory itself and the evidence 

 in support of it^ fully and clearly before the mind. 

 Thisj he ventures to submit^ has not yet been done ; 

 and to this circumstance he would attribute the posi- 

 tion which the theory at present holds. It appears to 

 him^ thatj while^ on the one hand, some supporters of 

 the theory have advanced arguments in its behalf 

 which are really untenable, so, on the other hand, 

 some of its opponents have erroneously imagined that 

 they had disproved the theory when they had merely 

 shewn the fallacy of those arguments. It appears to 

 him, likewise, that in respect both of the arguments in 

 support of it and of the arguments in opposition to it, 

 too much has been made of considerations connected 

 with the wood^ and too little of considerations con- 

 nected with the hud. The former, indeed, seem to 

 him extremely valuable, and he has taken full ad- 

 vantage of them in his argument. Yet it is rather 

 on the latter that he would rest the theory. The in- 



