AGENCY OF MAN. 113 



which is wholly barren, may have its fertility restored by the 

 addition of one per cent, of lime, or even a few bushels to the 

 acre. Another, which is acid, and therefore unfavorable to 

 vegetation, may by the addition of a single grain in a hun- 

 dred of some alkali, be made to yield forty, fifty, or a hundred 

 fold. 



Many a farm has remained for years barren, because its 

 electrical forces were not properly balanced, while the addi- 

 tion of some well-known substance, perhaps in the proportion 

 of not more than one grain in a million, would restore it to 

 fertility. It is said by certain medical practitioners, that a 

 millionth part of a grain of arsenic or opium, will act with 

 better effect upon certain diseases, than much larger quanti- 

 ties. This doctrine of the homoeopathist, applies with per- 

 fect truth to the application of certain salts to the soil. It is 

 often surprising to notice the effect of a single grain of lime 

 or potash in a hundred of the soil, doubling, tripling, and of- 

 ten quadrupling the quantity of the productions in a single 

 year. This result must be due, in part, to the electrical ef- 

 fect which this small addition produces ; hence we may learn 

 both the importance of ascertaining the composition of soils 

 by accurate analysis, and of improving them by adding those 

 substances which they require. 



In conclusion, it may be remarked, that the agents, consid- 

 ered in this and the preceding chapter, are not only the great 

 causes of change and reproduction in the vegetable, but also in 

 the animal and mineral kingdoms. Most of them are the natu- 

 ral powers ordained of God for the government of the natural 

 world. A correct knowledge of them will help us to explain 

 the almost infinitely varied and mysterious phenomena which 

 are every day presented to our minds ; and when we have 

 begun to understand their agency, when we can trace the 

 chain of effects to the ultimate cause we shall find, that they 

 will present subjects of deep and delightful reflection. 



They will enable us to gain a deeper and more profitable 

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