As we have already indicated, this statement in reference to "the last new thing" in ventilation is, to say the least, puzzling. It virtually asserts the instantaneous and complete mixture of cold air with air heated by and with the gaseous products of combustion, and a simultaneous and necessarily rapid diffusion throughout the entire space of the ward in St. George's Hospital; and that this rapid mingling, mixing movement of particles is done without any perceptible mingling, mixing process, or movement whatever! It thus virtually states that the rapid change of air which alone constitutes perfect ventilation is effected without any ascertainable movement of such air. If such concurrent phenomena be really, as stated, "matters of fact," and not, as we take them to be, the honest but erroneous belief of persons not accustomed to scientific and chemical research, we can only ejaculate like Dominie Sampson—"Pro-di-gi-ous!"
We have so far played the part of critic. We have stated the abstract requirements of perfect ventilation, and have assumed that such requirements are inapplicable to most modern houses. We have condemned the general ignorance and indifference to the proper supply of one of the essentials to existence, and have ridiculed the miserable expedients which pass current under false pretenses. We have further discussed the theory and practice of ventilation mainly distinct from its almost inseparable connection with house-warming. But, unless we are prepared to supply our houses by mechanical contrivances, such as fans, etc., it is impossible practically to consider the thing to be done apart from the obvious means to carry it out; and it is in heat that we find the ever-present and most applicable motive force. If we can give to our houses an average temperature of 55° with local exceptions somewhat in excess of this average, we make them, and particularly the lofty slip of building forming the common London street-house, into a warm air-shaft, having an upward draught. If we can properly arrange and control the entrances and exits of the necessary air, and secure that the supply be ample and the conditions of its motion innocuous, we have solved the problem of practical ventilation.
Any one who can effect this solution will be fairly entitled to the gratitude of all ranks and classes of society—excepting, perhaps, that of the medical profession! And whoever does this by a simple method—without using any scientific complications, and requiring no surrender of the average comprehension to the keeping of mechanical experts—who can reconcile sentiment with common-sense, and economy with the Epicureanism of our present civilization, and who yields no vantage-ground to servantgalism to demand higher wages, nor otherwise trenches upon the time-honored privileges of the servants' hall (to do little in the easiest way)—will have established a claim to social gratitude. The danger he will incur will be in the shape of a testimonial, which will most likely make Art shiver, and the descend-
