The first mention of the use of coal as fuel occurs in a charter of Henry III., granting licence to the burgesses of Newcastle to dig for coal. In 1281 Newcastle is said to have had some slight trade in this article. Shortly afterwards coal began to be imported into London for the use of smiths, brewers, dyers, soap-boilers, &c. In 1316, during the reign of Edward I., its use in London was prohibited because of the supposed injurious influence of the smoke. In 1600 the use of coal in the metropolis became universal; about 200 vessels were employed in the London trade, and about 200,000 chaldrons annually imported.
In 1848, however, there were, besides the railway-borne coals, 12,267 cargoes imported, or 3,418,340 tons. The London coal trade now employs 2700 vessels and 21,600 seamen, and constitutes one-fourth of the whole general trade of the Thames.
To understand the necessity for chimney-sweepers, and the extent of the work for them to do, that is to say, the quantity of soot deposited in our chimneys during the combustion of the three and a half millions of tons of coals that are now annually consumed in London, we must first comprehend the conditions upon which the evolution of soot depends, soot being simply the fine carbonaceous particles condensed from the smoke of coal fuel, and deposited against the sides of the chimneys during its ascent between the walls to the tops of our houses. These conditions appear to have been determined somewhat accurately during the investigations of the Smoke Prevention Committee.
There are two kinds of smoke from the ordinary materials of combustion—(A) Opaque, or black smoke; (B) Transparent, or invisible smoke.
A. The Opaque smoke, though the most offensive and annoying from its dirtying properties, is, like the muddiest water, the least injurious to animal or vegetable health. It consists of the particles of unconsumed carbon which have not been deposited in the form of soot in the flue or chimney. This is the black smoke which will be further described.
B. Transparent smoke is composed of gases which are for the most part invisible, such as carbonic acid and carbonic oxide; also of sulphurous acid, but smokes with that component are both visible and invisible. The sulphurous acid is said by Professor Brande to destroy vegetation, for it has long been a cause of wonder why vegetation in towns did not flourish, since carbonic acid (which is so largely produced from the action of our fires) is the vital air of trees, shrubs, and plants[58].
I may here observe, that several of the scientific men who gave the results of years of observation and study in their evidence to the Committee of the House of Commons, remarked on the popular misunderstanding of what smoke was, it being generally regarded as something visible. But in the composition of smoke, it appears, one product may be visible, and another invisible, and both offensive; while “occasionally you may have from the same materials varieties of products, all invisible, according to the manner to which they are supplied with air.”
The Committee requested Dr. Reid to prepare a definition of “smoke,” and more especially of “black smoke.” The following is the substance of the doctor’s definition, or rather description:—
1. Black Smoke consists essentially of carbon separated by heat from coal or other combustible bodies. If this smoke be produced at a very high temperature, the carbon forms a loose and powdery soot, comparatively free from other substances; while the lower the temperature at which black soot is formed, the larger is the amount of other substances with which it is mingled, among which are the following:—carbon, water, resin, oily and other inflammable products of various volatilities, ammonia, and carbonate of ammonia.