The foregoing statements as to the complex nature of the subject are intended to show that, if means for securing ventilation are to be employed beneficially, they must be applied with knowledge and be regulated with judgment; and also, that the ever-varying conditions and states of the outer atmosphere preclude the possibility of devising any appliance or apparatus by which constant and efficient ventilation can be automatically procured.

Advance will only be made by those who realize the necessity of pure air as a means of securing the health of individuals and communities, and who also acknowledge the intricacies of the subject, and insist upon the fact that constant individual attention is required (even when reasonable means are provided), if good ventilation is to be continuously secured. Those who have never studied the subject are ever the most ready to affirm that it is a very simple matter, and to condemn architects and builders for not providing everlasting means whereby, under the most varying conditions, a supply of fresh air, exactly to their liking, can be conveyed to them without trouble or further expense, regardless of the facts that the state of the atmosphere is constantly changing, that apartments are variously occupied, and that individuals are so constituted or affected by habit, that an atmosphere in which some can comfortably exist, is offensive or discomforting to others. This unreasonableness on the one hand, and on the other the persistency with which many disregard the necessary provision to secure ventilation, or even decline to provide for it because of the difficulties it presents, are responsible for retarding true progress in the matter.

To secure ventilation is much more than a personal undertaking, because it is useless to expect that good ventilation can be obtained unless the outer atmo-gpbere is in a state of purity; and although many things have been accomplished during the present century, in a communal manner, to make it more possible than it was to secure a sufficiently pure atmosphere in and around our dwellings, the fact still remains that, where communities are thickly congregated in cities and towns, constant vigilance is required on the part of Local Authorities to prevent the carelessness of some and the apathy of others jeopardizing the general health by uncleanliness, or by permitting the accumulation or discharge of im-puritit resulting from domestic requirements or manufacturing processes.

The Stale and Local Authorities have in recent years and in many ways attempted to prevent contamination of the outer atmosphere, by regulating the discharge of smoke and noxious gases, by preventing the pollution of streams, by drainage, by the removal of house-refuse, by the cleansing of eta, by regulating the keeping of animals in and about dwellings, and by the notification and isolation of infectious diseases; but there is still much that might be done, not only in the courts and alleys of cities and towns, but also in better-favoured localities and country places, before the outer atmosphere can at all times be considered reasonably pure and wholesome; and even when all has been done that can be expected of the State and of Local Authorities, it is still incumbent upon every individual, by habits of personal and domestic cleanliness, and by a knowledge and daily use of the means of ventilation, to safeguard both his own health and that of those residing around him. Regarded thus, ventilation is a collective as well as a personal matter.

If every individual appreciated the value to health which resulta from constantly breathing pure air, no cost would be spared in securing it; yet because the effects of living in an impure atmosphere are only at times, and by a few highly-sensitive people, made quickly known, the majority are callous, and begrudge the outlay and trouble which are necessary to supply then with wholesome air. They hourly take into their systems an insidious poison which, although it may be slow in its effects, will certainly cause suffering and prolmbly untimely death. Even those who would be disgusted at the idea of partaking of food not perfectly pure and fresh, or of drinking fluids which have become contaminated, and would on no account eat or drink what they knew had been near the lips of anyone else, will nevertheless be content to live in a close and unwholesome atmosphere, and freely breathe the air which has recently been respired by others, regardless of the consequences; and yet, because of the necessity of constantly supplying the lungs with air to sustain life, the large volumes of impure air inhaled will more surely undermine the constitution than the occasional partaking of food or drink, which to their sense of taste, sight, or smell, may appear to be contaminated.

Let us now consider what other conditions are requisite for the comfort of householders for whom ventilation is demanded. Buildings are ereceted principally as a protection from the ever-varying conditions of the atmosphere; this implies that comfortable ventilation is not at all times to be secured in the open, even presuming that the air is pure. If in the open we cannot secure comfort, and consequently build houses because at times movement of the atmosphere Lb too rapid, at other times too stagnant, now too hot and anon too cold, sometimes too dry and often too wet, it is evident that by enclosing a portion of the air within walls and roofs a risk is run of causing stagnation; free circulation at all events is impeded, and most of the influences, which outside are at work upon its purification and maintenance in an uniform state as regards composition, are shut out; hence the necessity for special means being provided whereby the air within buildings may be constantly changing, and maintained in a condition suited to the comfort and capable of sustaining the health of the inmates.