282 
On the Cultivated Potato. 
destroyed as soon as they became perceptible. An increased 
luxuriance now became visible in every plant, numerous 
blossoms were emitted, and every blossom afforded fruit." * 
Atmospheric influences must be touched upon. But I cannot 
undertake to deal with the gaseous envelope of this whirling 
world to which, coupled perhaps with electricity, we owe the 
occurrence of the weather phenomena that undoubtedly- aflfect 
in high degree the present subject of inquiry. I wish the 
Meteorological Society could help us. The atmosphere is a 
spheroidal stratum of uncertain height, 100 to 200 miles, con- 
centric with the earth and pressing heavily on it : a mechanical 
combination of nitrogen, oxygen, and carbonic acid, in which, 
like flocks in a sunbeam, animal and vegetable germs, seeds 
and spores, of disease and putrefaction, hover over all organic 
life and matter. How far do atmospheric influences stimulate 
these sometimes latent pests? I cannot answer this important 
question : but I was much struck at the time, as I am now 
impressed, by two lectures delivered by Professor Tyndall in 
January 7, 1876 : the first lecture, before the Royal Society, ' On 
the optical deportment of the atmosphere with reference to the 
phenomena of putrefaction and infection ;' the other, on ' Germs,' 
was given at the Royal Institution. I heartily wish we could 
enlist the learned Professor for the National cause in which we 
are now embarked. Air, he says, isolated ^and left at rest, is 
found to deposit its motes and to become pure : in this pure 
air tempting infusions remained intact, whereas similar infusions 
exposed in the open air, and owing to germs floating therein, 
swarmed with bacteria. From another experiment he inferred 
that germs hover in little clouds and settle at different times. 
Clouds of disease-germs may explain a puzzle to surgeons : why 
a wound, going on well for a while, should suddenly and without 
apparent reason become putrid ; it may be that it was dressed 
just as a germ cloud passed. According to Professor Tyndall, 
more than by battle, accident, or famine, humanity suffers from 
disease-germs conveyed in air and water. Green leaves in the 
sun absorb carbon and leave oxygen, and at night reverse the 
process. Increase of carbonic acid is dangerous to animals, 
deficiency injures vegetables. Atmospheric action, similar to 
that which produces influenza in man, is supposed by Liebig and 
Klotzsch to be the special cause of the potato-disease of 1845 : 
taken together, epidemic miasmata ; the wet summer of 1844 ; 
frost, March 1845 ; the great heat of forepart of that summer, 
and the uncommon luxuriance of the crop. The Highland 
Society's 'Transactions' for 1845 mentions disease at end of 
♦ ' On the inverted action of the Alhumous Vessels of Trees,' by T. A. Knight; 
printed, ' Philosophical Transactions, 1806,' p. 293-304. 
