V. ORIGIN OF MOULD. 207 
which, as we have already remarked, the origin 
of mould depends. 
The experiments were diverfified. Sometimes 
I covered a half, fometimes two thirds, or one, 
of a flice of bread, an apple, a pear, or a gourd, 
without touching the other half. The half, two 
thirds, or one third, were juft in the condition of 
the fown fubftances. I likewife made another 
experiment. After covering half a flice of bread, 
apple, or gourd, with duft, the furface fown was 
applied to another furface fimilar but unfown, 
and both left in this ftate feveral days. On the 
whole fown furface a veil of mould appeared, the 
vegetation of which had ceafed, becaufe it was 
fpoiled by the fubftance applied: but no veltige- 
of mould was feen onthe unfown part. Thus the 
hypothefis is corroborated, that the duft is the real 
feed of the mould, becaufe that produced on the 
places fown was exactly of the fame fpecies with 
what had afforded the duit. 
Notwithftanding all thefe plaufible and repeat- 
ed experiments, I was not fatisfied. Is it not 
‘pofible, faid ¥ to myfelf, that this duft only ren- 
ders the foil more fertile, fo that it will produce 
a greater quantity of mould, as the earth fertil- 
ized by foreign matter will produce more plants ? 
Certainly it was not impoffible; and, withing to 
proceed with philofophic ftrittnefs, I judged my- 
felf obliged to realize or remove the poflibility : 
for 
