authorities come to anything more than a substantial agreement. Local heat centres make currents of air producing winds; growth of vegetable life absorbing the carbonic acid thrown off by animal. life, and the falling rain washing out the poisoned impurities of the air, are among nature's principal and more potent methods of outdoor ventilation and purification.

The smoke chimney, with the fire on the hearth, for hundreds of years gave good ventilation (comparatively) to the dwellings of our ancestors, and, until the stove was invented, the want of none other was felt. With stoves and furnaces, with closed chimney drafts, came along fatally injurious, permanent diseases to the race. Hot air furnaces, as first introduced without ventilation, were next akin, in their pernicious effects, to the water closets and modern improvements connecting without traps directly with the sewer, and we believe no trap has yet been invented which will perfectly prevent the escape of sewer gas in a modernized building. Before the creation of such institutions as hospitals and asylums, only the criminal classes were congregated, and as the methods of punishment did not look to reformation, it is but of comparatively recent date that ventilation there has assumed a position of prominence and importance.

Nature's methods in vegetable and animal life require that the inferior and weak shall give place to the vigorous and strong,-in fact, in great measure, the latter absorbs and drowns the former; the law of the survival of the fittest runs through vegetable and animal and up into human life, controls customs and governments, and when human society is not influenced directly to the contrary by the teachings of Christianity, nature's methods are followed, and the decadence and extinction of the unfortunate children of sorrow and crime is not only not averted but hastened. The opinion obtains, to a considerable extent, that there is no demand for a better physical care for the occupants of prisons and asylums, but rather that society is bettered by suffering nature to apply its quickest methods for remedying the evil. A true Christianity regards the weaker as dependent upon, and needing the especial care of the stronger, and with emphasis demands improved environments for the unfortunate and criminally inclined to promote their rescue and reformation. Moral and spiritual development, to obtain foothold upon such natures, needs an improved physical basis.

The old-time prison, workhouse and poorhouse, simply perpetuating the existence of the dependent classes, without elevating them physically, morally and religiously, antagonizes good government and Christian civilization probably more than does nature's method, and there is hardly a question but that the Spartan rule of crushing down and tramping out is better than to stimulate and build up an ever increasing criminal race without improvement.

The unfortunates cast upon public care are being recognized as entitled to such consideration as will place them upon such a plane as to give promise of betterment; and one of the first steps in building up the physically and morally shattered, in hospitals and asylums is, better air; one of the first steps in reformation of the criminal and incorrigible is, to give a better and purer physical development on which to build moral and religious improvement. Foul air and foul lives are intimately connected in the nature of things. It is quite impossible to give statistics which show an improved moral and religious elevation, in figures, at a hospital or prison, growing out of the ventilation of the buildings, as such can be given in the cases of sickness and deaths; yet all persons, at all fit for their positions in charge of public institutions, know that healthy, cleanly surroundings help to develop the better parts of the nature of the inmates.

The effect upon the physical nature can be quite definitely shown. A report of the Board of Health shows that the thorough ventilation of the Boston City Hospital, from and after June, 1876, reduced the mortality rate in the wards of the hospital, for certain classes of cases occupying those wards, more than 50 per cent., and in other wards, with a still different class of cases, 71 per cent. Of two prisons in Vienna, one, being badly ventilated, lost 8 4-10ths per cent. of the prisoners by death annually, and one well ventilated lost per annum only 1 4-10ths per cent. It is within the personal knowledge of the writer that the death rate in a reformatory was brought down from an annual average of 1 45-100 per cent., for eight years, to 3-100 of one per cent. per annum for two years, after a ventilation, necessarily quite imperfect, was introduced in the building (no reasonable expense can make good ventilation in old buildings). A statement has appeared in print, that in an examination made in a large number of the public schools in Michigan within a few years, there was found to exist in the air 25 parts in 10,000 of carbonic acid. If one-fourth part

of the money spent in the ornamentation of those buildings had been expended judiciously in preparing suitable ventilation for them, very many less of the parents would have been deploring the overtaxing of their children in their studies. Many less of these would have been shattered in their constitutions than has been the case, an evil caused by their spending five to six hours of the day in such an atmosphere.

Doubtless all the members of this Conference know the workhouse smell, that which meets them on crossing the threshold of more than one-half of the public institutions of the country. Whenever this villainous smell is encountered an indictment should be drawn against the managers of such institution, and they be held up before the bar of public opinion. No abatement of judgment should be allowed until they could transfer the blame rightfully to other shoulders. Boards of Health should be clothed with the necessary powers to correct the evil and prevent a recurrence; physical, mental and moral decay is in every breath of this perfume.

This execrable smell is caused in great measure by the animal exhalations from the breath, skin and body, in crowded rooms with stagnant air; the poison settles in moisture on the walls and furniture, and forms a coating of glutinous organic matter dried on from time to time, and constantly increasing. Mopping or wiping over of floors and furniture while the buildings are constantly occupied increases the bad effect, as moisture increases the virulence of the effluvia. Sore eyes, erysipelas, opening of scrofulous sores, diphtheria, slow fevers, zymotic diseases, all, when introduced in such places, stay well.

In speaking of the methods of artificial ventilation, of the volume of air requisite,―of the measurements and movements of air and gasses,-when figures are resorted to, it is to be understood that approximation to correctness is all that can be arrived at. Authorities differ in most cases, and sometimes very widely; this comes from the multitudinous changes and phases of nature,— changes which affect all experiments and shade all facts.

Natural ventilation is continually taking place, through the walls, in all habitable rooms, to greater or less extent, and to a far greater degree than is easily recognized. This shows artificial ventilation to be more necessary when occupied rooms are separated only by walls from other occupied rooms; Pettenkofer shows

from experiments made, that in the case of an ordinary brick building with outside exposures, making the test with the temperature inside and outside ranging 30 degrees, the air was changed once in 60 minutes; with a fire burning in the stove, once in 45 minutes; with all cracks tightly pasted up, once in 80 minutes; with the difference in temperature greater, the change would be more rapid. We can readily see that with the air outside below zero, and a comfortable warmth inside, the change would be very rapid; the briskness, or force of the wind, and thinness or greater permeability of walls, all enter into consideration.

In applying any system of artificial ventilation, the ventilation that nature enforces should be duly considered, and the difficulty of applying artificial ventilation to large, complex buildings, with rooms for different purposes, of different sizes, and of different exposures, should be thoroughly considered by boards and archi

tects.

Hot air flues for admitting air, and foul air flues for its exit, should vary as the circumstances require; flues and pipes for outflow should be larger than those of inlet, to offset cooling effect and admission of air by cracks and the opening of doors. The air in a room should be changed about once in thirty minutes, in crowded rooms, oftener; a room should be considered crowded, in which there is less than 600 cubic feet of space to each healthy occupant, or than 1,200 to each patient, or person physically defective; if complete cleanliness of room and furniture is not observed, space and air should be increased. It becomes injurious to persons except in very robust health, to change the air oftener, as drafts become unavoidable; soon as the movements of the air become perceptible to persons in delicate health, they are injured-; the effect of drafts in an enclosed room (and especially of a crowded one), are entirely different from currents of air outdoors. We can readily see that in a room with fire in a fireplace, or with a hot stove, where one must needs frequently turn around because too hot on the side next the fire, and too cold on the opposite, the person is in exposure to colds from too much ventilation; drafts must be avoided on the one hand, and stagnant, or too sluggish movement of the air on the other.

In planning any building, the fireplace may be introduced, as a positive advantage, that will injure but little any system used; at certain times and seasons, the fireplace may be used alone, giving

entirely satisfactory ventilation; but the chimney draft to a fireplace is, under some conditions of the barometer, valueless, and therefore, for buildings for congregate life, it can only supplement other devices; there is greater loss of heat by fireplace than by any other method, therefore, it is too expensive for constant use in cold climates.

There are two principal forces used in ventilation, one by pulsion, or forcing air into a room or building, the other by aspiration, or drawing it out; either may be very defective when not combined with the other, and yet costly attempts at ventilation are made by one or the other methods alone. We see, frequently, expensive buildings planned by architects, with cold flues, to ventilate by aspiration, when warmth was supplied to the rooms by connection, or radiation from stoves or steam coils; such flues not being simply useless, are frequently injurious, because under certain conditions they pass air into the room through the foulness that has accumulated in the flues. Nothing should really be entitled to the name of ventilation that does not combine pulsion and aspiration.

There is a waste in any building, of whatever cost or pretensions, in which the warmth caused by the smoke chimney is not utilized for ventilation by aspiration.

When mechanical appliances cannot be brought into use, one of the best ventilations now practicable is that by which a furnace is used to warm the air which forces itself into the rooms. While the heat from the smoke chimney heats the air in the foul air shaft, causing the outflow by aspiration; as the latter power will ordinarily be more deficient, the higher the chimney the more satisfactory will be the result. The smoke flue inside the chimney, if of iron, will be more efficient in its action on the ascending air, but will soon be eaten up by corrosion; cement, or earthen pipe, is next in effectiveness; the loss in aspirating power is very great if brick flues are used.

When the steam boiler comes into use, for supplying water, hot and cold, in the building, the steam can be used not simply for pumping and heating water, but also for heating coils for warming the air in rooms by direct radiation, or preferably by indirect heating a room or reservoir, and thence to be distributed by flues and pipes where needed; also, by heating coils in the foul air shafts, causing aspiration. This system is preferable to the furnace,