THE ESSENCE OF HUMANITY. 219 



aqueducts, of canals, of railroads, of telegraphs, merely presents 

 successive phases of that development of the surface of the 

 globe due to man — a development which is affected under his 

 self-conscious or rational agency, in obedience to his Maker's 

 command " to replenish the earth, and subdue it." It may 

 here be observed, that while the animal is merely enabled, 

 with its specific physical strength, to provide its means of 

 subsistence ; man is enabled as he advances in his work of 

 subjugating the earth, to avail himself of external material 

 force to effect his successive purposes. Under the guidance 

 of his rational intelligence, he proceeds on mechanical princi- 

 ples, he collects and concentrates for the ends he has in view, 

 the forces involved in gunpowder and steam, and thus making 

 his way into the interior of the earth in search of its mineral 

 wealth, modifies its surfaces, in accordance with the re- 

 quirements of each locality. It must be quite clear to every 

 unprejudiced thinker that human agency is destined to effect 

 extraordinary changes in the arrangements and aspect of the 

 surface of the globe. 



12. The proper conception of the nature and effects of those 

 cosmical changes induced by man, may be indicated in the 

 following considerations : — 



1st, That the full development of man's material economy 

 and welfare on earth, is only secondary to the higher purposes 

 of his existence. 



2d, That the full development of man's material economy 

 and welfare, including his full legitimate enjoyment thereof, 

 is to be worked out by him in evidence of the amount of 

 know ledge to which he has attained of the lawsofdod in 

 nature, of the extent to which he has properly applied and 

 enjoyed thai amounl of knowledge to which he has attained, 

 through the -ill of that rational consciousness conferred on 

 him as a pari of his human constitution. This principle 



involves the proper use of man's intellectual faculties and 



