[21] The water (which passes off in imperceptible vapour) is generated by part of the oxygen of the air uniting with part of the hydrogen, which forms the great bulk of the coal-gas: and the carbonic acid gas is produced by the union of another portion of the oxygen uniting with the smaller portion of carbon, which is the other component part of the coal-gas. [22] 100 Cubic inches of carburetted hydrogen from coal, require for burning 220 cubic inches of oxygen and produce 100 cubic inches of carbonic acid--100 cubic inches of the same gas obtained from wax, require for burning 280 cubic inches of oxygen and produce 137 cubic inches of carbonic acid--100 cubic inches of the same gas procured from lamp-oil, require 190 cubic inches of oxygen for burning, and produce 124 cubic inches of carbonic acid. The following lines relating to the salubrity of the gas-light illumination are copied from Mr. Lee’s evidence in the House of Commons, when examined on that subject. Question--“Is the health of your manufacturers at all affected by the use of gas?--Answer--Not in the least, or I would not have adopted it. I believe I explained to the Committee, that I used the gas-lights in my own house first.” Q. “You have not seen the smallest alteration in the health of your workmen?--A. Not in the least, for had I seen it, it would have been a fatal objection to it.” Q. “And you say the same in regard to the use of the gas-lights in your own family?--A. Certainly I do.” As to the brilliancy of the flame, an appeal may be made to every one who has witnessed the gas-light illumination, whether it be not superior to the best wax candle-light, or the light of Argand’s lamps. It may be described as a rich compact flame, burning with a white and agreeable light. It is also perfectly steady, when the flame is limited to a moderate size: in large masses, it is subject to that undulation which is common to it with all flames of certain dimensions, and is caused by the agitation of the surrounding atmosphere. The gas flame is entirely free from smell. The coal-gas itself certainly has a disagreeable foetid odour before it is burnt, so has the vapour of wax, oil, and tallow, as it comes from a lamp or candle newly blown out. This concession proves nothing against the flame of gas which is perfectly inodorous, a white handkerchief, passed repeatedly through it and applied to the nose, excites no odour.