These experiments are of the gravest import, as they show more clearly than has ever been done before the absolute necessity for special and perfect ventilation where coal gas is employed for the illumination of our dwelling rooms.
When coal gas was first employed during the early part of this century as an illuminating agent, the low pitch of the old fashioned rooms, and the excess of impurities in the gas, rendered it imperative that the products of combustion of the sulphur-laden gas should be conducted from the apartment, and for this purpose arrangements of tubes with funnel shaped openings were suspended over the burners. The noxious gases were thus conveyed either to the flue or open air; but this type of ventilator was unsightly in the extreme, and some few attempts were made to replace it by a more elegant arrangement, as in the ventilating lamp invented by Faraday, and in the adaptation of the same principle by Mr. I.O.N. Rutter, who strove for many years to direct attention to the necessity of removing the products of combustion from the room. But with the increase of the gas industry, the methods for purifying the coal gas became gradually more and more perfect, while the rooms in the modern houses were made more lofty; and the products of combustion being mixed with a larger volume of air, and not containing so many deleterious constituents, became, if not much less noxious, at all events less perceptible to the nose. As soon as this point was reached, the ventilating tubes were discarded, and from that day to this the air of our dwelling rooms has been contaminated by illuminants, with hardly an effort to alleviate the effect produced upon health. I say "hardly an effort," for the Messrs. Boyle tried, by their concentric tube ventilators, to meet the difficulty, while Mr. De la Garde and Mr. Hammond have each constructed lamps more or less on the principle of the Rutter lamp; but either from their being somewhat unsightly, or from their diminishing the amount of light given out, none of them have met with any degree of success. In places of public entertainment, where large quantities of coal gas are consumed for illuminating purposes, the absolute necessity for special ventilation gave rise to the "sun burner," with its ventilating shaft. This, however, gives but a very poor illuminating power per cubic foot of gas consumed, due partly to the cooling of the flame by the current of air produced, and partly to its distance from the objects to be illuminated.