REACTION OF MAN ON NATURE. 9 



means complete enough to warrcint me in promising any approach 

 to fulness of statement respecting them. Systematic observation 

 in relation to this subject has hardly yet begun, and the scattered 

 data which have chanced to be recorded have never been collected. 

 It has now no place in the general scheme of physical science, and 

 is matter of suggestion and speculation only, not of established 

 and positive conclusion. At present, then, all that I can hope is 

 to excite an interest in a topic of much economical importance, 

 by pointing out the dii*ections and illustrating the modes in which 

 human action has been, or may be, most injurious or most bene- 

 ficial in its influence uj)on the physical conditions of the earth we 

 inhabit. 



We can not always distinguish between the results of man's ac- i 

 tion and the effects of purely geological or cosmical causes. The » 

 destruction of the forests, the drainage of lakes and marshes, and 

 the operations of rural husbandry and industrial art, have un- 

 questionably tended to produce great changes in the hygrometric, 

 thermometric, electric, and chemical condition of the atmosphere, 

 though we are not yet able to measure the force of the different 

 elements of disturbance, or to say how far they have been neutral- j 

 ised by each other or by still obscurer influences ; and it is equally 

 certain that the myriad forms of animal and vegetable life, which 

 covered the earth when man first entered upon the theatre of a 

 nature whose harmonies he was destined to derange, have been, 

 through his interference, greatly changed in numerical proportion, 

 sometimes much modified in form and product, and sometimes 

 entirely extirpated.* 



* Man has not only subverted the natural numerical relations of wild as well 

 as domestic quadrupeds, fish, birds, reptiles, insects, and common plants, and 

 even of still humbler tribes of animal and vegetable life, but he has effected, 

 in the forms, habits, nutriment and products of the organisms which minister 

 to his wants and his pleasures, changer^ which, more than any other manifesta- 

 tion of human energy, resemble the ex/. "cise of a creative power. Even wild 

 animals have been compelled by him, tu^ough the destruction of plants and 

 insects which furnished their proper aliment, to resort to food belonging to 

 a different kingdom of nature. Thus a New Zealand bird, originally gran- 

 ivorous and insectivorous, has become carnivorous, from the want of its natural 

 supplies, and now tears the fleeces from the backs of the sheep in order to 

 feed on their Mving flesh. 



All these changes have exercised more or less direct or indirect action on 



