Preface. | XV 
_Terms are used in the following account of 
the gypsum, without nice attention to their force; 
as it is difficult more accurately to express our 
present ideas. The plaister, is, for instance, called 
a stemulant, a manure. Some substances are said to 
make a good footing for the plaister, that it wants 
something to feed on, &c. When we know more 
about it, we can establish a more appropriate and 
correct phraseology. 
Several to whom I have applied for informa- 
tion have not favoured me with it, from a disin- 
clination, I presume, to throwing their thoughts 
on paper. This discouraged me from extending 
my correspondence. But I believe I have obtain- 
ed the most material facts. Those who have an- 
swered the queries, occupy land of every variety 
of description, so as to comprehend the whole 
range of the different soils on which the plaister 
is used. 
I shall be truly grateful, if any of those who 
have been in the practice of applying the plaister, 
will supply omissions, and rectify mistakes. 
I indulge a hope that men of chemical and 
philosophical knowledge, will be induced farther 
to examine and analyze this powerful substance, 
with a view more accurately to discover its agri- 
cultural properties, and the causes of its operation 
on plants. The farmer, when taught by their dis- 
