26 
CAUSES INTERFERING WITH 
sphere is so highly charged with noxious matters, 
that many deciduous plants and almost all ever- 
greens cease to flourish, or exhibit only a sickly 
vegetation. 
“ In an interesting biographical sketch of his 
lamented friend, Dr. Turner, Professor Chris- 
tison confirms, by subsequent experience, the 
opinion formerly given respecting the noxious 
operation of the sulphurous or muriatic acid 
gas upon plants. He describes their action as 
so energetic, that, in the course of two days, the 
whole vegetation of various species of plants 
may be destroyed by quantities so minute as to 
be altogether inappreciable by the senses. On 
two occasions he was able to trace the identical 
effects of the same kind of works (the black ash 
manufactory) on the great scale, which his friends 
and himself witnessed in their researches. In 
one instance, the devastation committed was 
enormous, vegetation being, for the most part, 
miserably stunted, or altogether blasted, to a 
distance of fully a third of a mile from the works, 
in the prevailing direction of the wind. Against 
the evils arising from such a vitiated atmosphere, 
the plan of Mr. Ward provides effectual protec- 
tion, as the success of his own establishment 
amply demonstrates.” 
I believe, that there does not generally exist 
