a
fruitful cause of those thick black fogs with which town-dwellers are so
familiar. Sulphuretted hydrogen (H_{2}S) is a gas well known to students
of chemistry as a most powerful reagent, its most characteristic external
property being the extremely offensive odour which it possesses, and
which bears a strong resemblance to that of rotten eggs or decomposing
fish. It tarnishes silver work and picture frames very rapidly. On
combustion it changes to sulphurous acid (SO_{2}), and this in turn has
the power of taking up from the air another atom of oxygen, forming
sulphuric acid (SO_{3} + water), or, as we more familiarly know it, oil
of vitriol.

Yet the smoke itself, including as it does all the many impurities which
exist in coal, is not only evil in itself, but is evil in its influences.
Dr Siemens has said:--"It has been shown that the fine dust resulting
from the imperfect combustion of coal was mainly instrumental in the
formation of fog; each particle of solid matter attracting to itself
aqueous vapour. These globules of fog were rendered particularly
tenacious and disagreeable by the presence of tar vapour, another result
of imperfect combustion of raw fuel, which might be turned to better
account at the dyeworks. The hurtful influence of smoke upon public
health, the great personal discomfort to which it gave rise, and the vast
expense it indirectly caused through the destruction of our monuments,
pictures, furniture, and apparel, were now being recognised."

The most effectual remedy would result from a general recognition of the
fact that wherever smoke was produced, fuel was being consumed
wastefully, and that all our calorific effects, from the largest furnace
to the domestic fire, could be realised as completely, and more
economically, without allowing any of the fuel employed to reach the
atmosphere unburnt. This most desirable result might be effected by the
use of gas for all heating purposes, with or without the additional use
of coke or anthracite. The success of the so-called smoke-consuming
stoves is greatly open to question, whilst some of them have been
reported upon by those appointed to inspect them as actually accentuating
the incomplete combustion, the abolition of which they were invented to
bring about.

The smoke nuisance is one which cuts at the very basis of our business
life. The cloud which, under certain atmospheric conditions, rests like a
pall over our great cities, will not even