300 
Though it is not generally known, yet a series 
of experiments has been carried on for a great 
length of time in this country upon the operation 
of gypsum as a manure. The Berkshire and the 
Wiltshire peat-ashes contain a considerable portion 
of this substance. In the Newbury peat-ashes I 
have found from one-fourth to one-third of gypsum; 
and a larger quantity in some peat-ashes from the 1 
neighbourhood of Stockbridge : the other consti- 
tuents of these ashes are calcareous, aluminous, 
and siliceous earth, with variable quantities of sul- 
phate of potassa, a little common salt, and some- 
times oxide of iron. The red ashes contain most 
of this last substance. 
These peat-ashes are used as a top-dressing for 
cultivated grasses, particularly sainfoin and clover. 
In examining the ashes of sainfoin, clover, and rye 
grass, I found that they afforded considerable quan- 
tities of gypsum ; and this substance, probably, is 
intimately combined as a necessary part of their 
woody fibre. If this be allowed, it is easy to ex- 
plain the reason why it operates in such small 
quantities ; for the whole of a clover crop, or sain- 
foin crop, on an acre, according to* my estimation, 
would afford by incineration only three or four 
bushels of gypsum. In examining the soil in a 
field near Newbury, which was taken from below 
a footpath near the gate, where gypsum could not 
have been artificially furnished, I could not detect 
any of this substance in it ; and at the very time I 
collected the soil, the peat-ashes were applied to 
the clover in the field. The reason why gypsum 
is not generally efficacious, is probably because 
