242 
THE SMOKE ABATEMENT EXHIBITION. 
except little children under five years of age, and these are 
nearly free owing to their being kept indoors, when they are 
not so subject to its influence. The action of fogs is thus 
explained by Dr. Frankland. The coal burnt in London gives 
off large quantities of oily products. These float in the air and 
surround the small particles of vapour which constitute fog, 
preventing them from either evaporating or coalescing. Thus 
an impenetrable barrier is formed, which entangle and become 
impregnated with the noxious gases given off by the combustion 
of coal. The fog acts thus in two ways. In the first place, 
instead of pure air we breathe other gases, which, even if they 
were not positively harmful, would be objectionable owing to 
their inability to carry on the process of respiration. Hence 
even in a sea fog, which is free from deleterious vapours, there is 
a sense of oppression owing to the incomplete action of the 
lungs. But, in the second place, the fogs of London are charged 
with noxious vapours, which are in the highest degree injurious. 
During one of the late fogs, a chemist in the City of London, 
made analyses of the amount of carbonic acid in the air, and he 
found that it rose as high as 12 parts in 10,000, 4 parts in 
10,000 being the usual amount, and 6 parts being declared by 
physiologists to be the greatest amount that can be present in an 
atmosphere without producing evil consequences to those breath- 
ing it. These facts need no comment. They shew the 
necessity for the application of remedial measures. The recent 
Exhibition has shewn the difiiculty that there is not only in 
devising the measures, but even in determining in what directions 
to look for them. But, although no very great results are likely 
to result from it, it will have done a great service in directing 
public attention to this most serious evil, for we know certainly, 
that the first step towards the abolition of a mischief is the 
clear perception of its existence, its magnitude, and its disastrous 
consequences. 
