we . ORIGIN OF MOULD. 205 
the third day, both were covered with mould; 
but that on the fown fubftance was almoft.double 
the height and thicknefs of the mould on the 
other. Both {pecies were the fame, and perfedly 
fimilar to what had produced the duft. On the 
fourth day, the mould of the unfown fubftance, 
though not fo thick, was equal to the other in 
height ; it was even higher the following day, 
but afterwards continued to. become thinner. 
‘Thefe experiments were repeated eleven times on 
moiftened bread: twice the mould became e- 
qually high and thick on both fubftances, and 
nine times it was higher on the unfown one, but 
‘thinner. It conftantly fprung firft on the fown 
fubftance. 
_ Having collegted a great quantity of ripe duft, 
I thought of varying the portions fcattered on 
moiftened bread. ‘The confequences were new:: 
When the quantity of duft was very fmall, there 
was almoft no difference in the height and thick. 
nefs of the mould on either fubftance fown or 
unfown; however, the thicknefs increafed. by 
fowing a greater quantity, and it was never fo 
thick as when liberally ftrewed over the bread: 
then the mould was a real covering ; but in pra- 
portion as the thicknefs augmented, the height 
diminifhed. The experiments were repeated 
again and again on apples, pears, and gourds ; 
and 
