On Mildew. 167 
My fixed opinion then is, and long has been (in 
which I since find I agree with the famous M. Chateau- 
Vieux) that the powder which forms the rust, called 
mildews, is the extravasated juice of the plants dried hie, 
the sun, upon the stalk. 
My reasons are these, Ist. The grain, we see, re- 
ceives no more nourishment after it is violently struck. 
2d. On a careful inspection, it appears that some of 
these rusty blisters are actually under the outer coat or 
skin of the stalk, and do not appear to have any com- 
munication from without, others are only split in the 
middle, some more and some less, and the rust appears 
on the outside more or less according to the opening. 
3d. The learned Mr. Tillet (Duhamel tells us) with a 
good microscope, actually saw the juice issuing from 
these small openings, over which he still perceived some 
pieces of the membrane which imperfectly covered 
them. This methinks must give occular demonstration. 
But the two former satisfied me, the second especially 
appeared demonstrative. 
The true cause of this extravasation is next to be in- 
quired into. This no writer that I know of has hinted. 
I take it to be this, @ sudden obstruction of the juices of 
the plant, by a very cool night, after several days and 
nights of very warm weather. 
By a continued heat, the earth is warmed to a great 
degree, and all nature invigorated; this occasions a 
sreat ascent of the juices, so that every vessel is full 
{as in an animal of a plethorick habit when all know 
there is most danger of the vessels bursting ;) a sudden 
cold ensuing at this critical season chills. the tender 
ad 
