52 On Gypsum. 
contrary to theory it may be, my experiments have not 
“satisfied me that it is less nutritive to the earth, espe- 
cially when well clothed with these vegetables until to- 
wards the end of the winter. This cover added to the 
exclusion of the hoof, keeps its pores open longer in 
winter to the action of the atmosphere, than ploughing 
itself; and defends it against sun as wellas frost, whilst 
ploughing exposes it to both, my idea is, that this sys- 
tem is fitted for a combination with gypsum, and that 
such a combination may possibly succeed without the 
aid of manure. Ifso, it may be useful towards diminish- 
ing the deficiency of that article, for I agree with you, 
that nothing can be a complete substitute for it. To 
make the experiment fairly, I have set aside 200 acres, 
half to be cultivated in corn yearly, half to lie unculti- 
vated and ungrazed, and the whole to receive an annual 
dressing of three pecks of plaister to the acre. The repe- 
tition of the culture being too quick for a perennial 
plant, I use the bird-foot clover as we commonly call it, 
to raise clothing for the land, having found that the 
plaister operated as powerfully on that as on red clover. 
This grass rises early, dies soon in the summer, abounds 
in seed so as to set the land thick the following year, af- 
fords a good cover, and nourishes a second annual, the 
crab grass,* which springs through it the latter end of 
the summer, and gives a fresh cover to the earth. This 
experiment of combining the use of plaister with enclos- 
ing has hitherto been very flattering. 
As to corn stalks, for about 26 years past I have re- 
% Syntherisma Serotina L. 
