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.

The great difficulty which in the whole history of ventilation has opposed itself to the adoption of proper arrangements for removing the products of combustion has been the necessity of bringing the tube to carry off the gases low down into the room, and of incasing the burner in such a way that none of the products should escape; but with the present revolution in gas burners this necessity is entirely done away with, and the regenerative burner offers the means not only of removing all the products of combustion but also of effecting thorough ventilation of the room itself, as experiments made some few years ago showed me that a ventilating regenerative burner, burning 20 cubic feet of gas per hour and properly fitted, will not only remove all its own products of combustion, but also over 5,000 cubic feet per hour of the vitiated air from the upper part of the room.  I am quite aware that many regenerative lamp makers raise various objections to fitting ventilating lamps, these being chiefly due to the fact that it requires considerable trouble to fit them properly; but I think I have said enough to show the absolute necessity of some such system, and when there is a general demand for ventilating lamps, engineering skill will soon find means to overcome any slight difficulties which exist.

Having disposed in a few words of a subject which, if fully treated, would occupy a long course of lectures by itself, I will pass on to the consideration of gas as at present used as a fuel.