On Gypsum. 77 
tem of Malthus is overturned, more easily than the sys- 
tem of Malthus overturned the system of Godwin.” 
“The heavier the crop no matter of what, the richer 
the land is left, though the crop is taken off: From this 
fact stated by judge Peters, I infer, ‘‘ that the heavier 
the crop, 70 matter of what, the richer the land is left, 
if the crop is not taken off?’ Ifa heavy crop of weeds or 
crab grass (no matter of what) would leave the land 
richer though taken off, it will I suppose enrich it still 
more, when restored to the earth. By the fertility of 
the surface of the earth of uncultivated countries, and 
of long enclosed spots, our attention is drawn, to vege- 
table matter. The famous experiment of the willow, 
with many others, proves that vegetables draw much of 
their food from air and water. Whatever of these tran- 
sient elements, vegetables can catch and bestow on the 
earth, elaborated into a durable manure, seems to me to 
be a particular acquisition drawn from an inexhaustible 
treasury. It is however, not the small neat husbandry 
of which the judge is so justly enamoured, and which 
may be preferable in well peopled regions, but one cal- 
culated to improve a great space of worn out land slow- 
ly and at small expence. Weeds and grasses of all kinds 
undoubtedly injure the crops with which they grow, 
yet we sow clover with wheat. In seasons favourable to 
its growth, I have seen it injure wheat materially. It is 
for the purpose of replenishing the earth with vegetable 
matter that we do this. ‘The stubble and roots, the litter 
it produces or saves when fed away (such as straw and 
stalks) conspire to furnish the recruiting pabulum. 
Weeds and grasses of all kinds left on the surface or 
ploughed in, like wheat straw, are supposed by the en- 
