INTRODUCTION. 
XXlll 
of the sulphurous aud muriatic acid gases on plants ; he 
describes their action as so energetic, that, in the course of 
two days, the whole vegetation of various species of plants 
may he destroyed by quantities so minute as to he 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 
friend and himself witnessed in their researches. In one 
instance, the devastation committed was enormous, vegeta- 
tion being for the most part miserably stunted, or blasted 
altogether, to a distance of fully a third of a mile from the 
works, in the prevailing dnection of the wind.” 
Mr. Ellis’s is an extremely pleasing and well-wiitten 
papery it is full of very valuable information, collected 
with industry, and arranged with care ; the experiments to 
which he refers are of undoubted authority, and strictly 
applicable to general principles in the way intended by their 
various authors. I think they will he received as conclusive 
by that large class of readers which prefers the dictum of 
a philosopher to the fatigue of inquiry ; hut never by that 
limited class — that troublesome and inquiring class — which 
takes nothing for granted, which, in reading a well-arranged 
and instructive series of illustrations, argumentatively ap- 
plied, is continually asking, Quo tramite tendis ? ” And 
when, at length, the goal is discovered to which Mr. Ellis 
is conducting it — when he briefly concludes, Against the 
evils arising from such a vitiated atmosphere, the plan of 
Mr. Ward provides effectual protection, as the success of 
his establishment amply demonstrates,” then this little jury 
