THE MANSE GARDEN. 129 



nothing more is needful to a vigorous growth than 

 the proper supplies of heat and moisture inferring, 

 at the same time, that all manures are serviceable 

 only in so far as they give the land an aptitude for 

 the retaining of moisture and heat. But whilst they 

 bury thermometers and hygrometers at various depths, 

 for the purpose of experiments, they overlook those 

 phenomena which take place above ground, and which 

 are sufficient to establish the fact, that by repose the 

 soil is strengthened for the labour of future produc- 

 tion. Hence the well ascertained benefit of a suc- 

 cession of crops; hence the law, that when an old 

 forest dies out, and nature is left to herself, trees of 

 the same kind do not spring up in room of the de- 

 cayed ; and hence the fact now becomes appalling to 

 the husbandman, that in many places where it has 

 been too often sown on the same ground, though 

 heat and moisture be in all respects the same as in 

 former times, red clover almost refuses to grow. 



A new trenching of the ground once in eight or 

 ten years, in respect of giving newness and fresh- 

 ness to the soil, is equal to an eight or ten years' 

 fallow a mode of renovation which would be death 

 to man ; whereas trenching both renovates the soil 

 and* continues the supplies of human wants. There 

 can be no doubt that some advantage is gained also 

 by burying the larvae of countless insects ; for whilst 

 the leaves of plants in other parts of the garden are 

 eaten and decayed, every blade on the newly trenched 

 ground is green and entire. Trenching furnishes 

 an exclusive system of production, leaving nothing 

 on the surface but what the cultivator designs. An- 

 nual weeds are scarcely to be noticed as an exception, 



F2 



