THE POTATO-DISEASE. 295 
during very hot and dry summers, that the leaves 
of Lime-trees have become covered with a thick 
and sweet liquid, and in such quantity that for 
several hours of the day it ran off the trees like 
drops of rain. Many pounds might in fact 
have been collected from one tree; the juice con- 
tained sugar. We can scarcely assert, however, 
that these diseases are such as are calculated 
to shorten the life of the plant, excepting so far 
as they shew that it is an unhealthy condition. 
The terrible Potato-Disease has been variously 
accounted for, but still remains inexplicable. 
Some singular circumstances have been mentioned, 
as to its appearing in certain fields of particular 
districts of the country, very shortly after the 
appearance of thick, peculiar clouds of fog. 
From which it has been supposed that the fog 
must have contained some unusually destructive 
ingredient. How far this conjecture is sufli- 
cient to explain all the phenomena attendant 
on this visitation, we are not here able to say. 
Others believed that it was produced by the 
attacks of insects; which certainly was quite in- 
correct. Many chemists believed it to be owing 
to bad agricultural management; and others at- 
Q 
