XLII. 



THE MODIFICATIONS OF THE EXTEENAL 



ASPECTS OF ORGANIC NATURE PEODUCED 



BY MAN'S INTEEFEEENCE, 



A LECTURE DELIVERED BEFORE THE ROYAL GEOGRAPHICAL 

 SOCIETY, MAY Id, 1 879. 



The modifications of the external aspects of organic nature pro- 

 duced by man's interference form so large a part of the results 

 of all human activities whatever, that the very first thing to be 

 said in a single evening's lecture on the subject should consist 

 in a specification of the particular spots in that vast area which 

 the speaker proposes to touch upon. I propose, then, with your 

 permission, firstly, to glance at certain of the alterations, positive 

 and negative, in the landscape of our own country, which we 

 ourselves and our fathers before us have intentionally or un- 

 intentionally produced ; secondly, to notice a few of the many 

 alterations produced by disforesting in our own and other coun- 

 tries ; and thirdly, to show what our knowledge as to the localities 

 to which the parent stocks of the majority of our domestic animals 

 and of our cultivated plants may be assigned, implies, as to the 

 modifications of other regions of the world's surface which man has 

 produced by his processes of importation and acclimatisation. Eoom 

 may perhaps be found for a few speculations as to the future after 

 these details as to the past and present. 



I do not propose to enter into the large question of the extent 

 to which man may, with any propriety, be spoken of, as he has 

 been, as a ^ geological agency/ a ^ telluric ' or a ' cosmic ' agent ; 

 and I will at this very outset of my lecture profess that I think 

 man's power of modifying the climate of the earth upon which he 

 lives must be considered S when all the facts of the case are taken 



1 Upon this large question, one only of many large questions which the various 

 details of this subject suggest, and by which, even when most in the concrete, they 



3D 



