24 
CAUSES INTERFERING WITH 
paper published in the “ Gardener’s Magazine ” 
for September 1839, and as the subject is one 
of great importance, it being impossible to apply 
remedies without knowing the nature of the 
disease, I shall discuss it at some length. Mr. 
Ellis says that the real mode in which such an 
atmosphere proves injurious to vegetation was 
first shown by the experiments of Drs. Turner 
and Christison, which were published in No. 
XCIII of the “ Edinburgh Medical and Sur- 
gical Journal.” They ascertained that it is not 
simply to the diffusion of fuliginous matter 
through the air, but to the presence of sul- 
phurous acid gas, generated in the combustion 
of coal, that the mischief is to be ascribed. 
When added to common air in the proportion of 
1 -9000th or 1-1 0,000th part, that gas sensibly 
affected the leaves of growing plants in ten or 
twelve hours, and killed them in forty-eight 
hours or less. The effects of hydrochloric or 
muriatic acid gas were still more powerful, it 
being found that the tenth part of a cubic 
inch, in 20,000 volumes of air, manifested its 
action in a few hours, and entirely destroyed the 
plant in two days. Both these gases acted on 
the leaves, affecting more or less their colour, 
and withering or crisping their texture, so that 
a gentle touch caused their separation from the 
