is little or no diffusion through the walls, except that due to the difference of temperature, which may, in practice, be neglected.

draughts, even when the window is made as nearly as possible air-tight.*

The most simple method of ventilation is to (2) Cracks and crevices. Even in well-built allow the heated vitiated air to escape by openhouses the effect of the shrinkage of woodworkings near or in the ceiling, while fresh air is is soon seen; window sashes rattle, doors are out of line, and daylight can be seen between them and their frames, while the currents of air are easily noticed. These troubles are partially remedied by wedging the window sashes against their frames from the inside, the use of sand bags and weather strips

*

admitted below (upward system). The cooling effect of walls and windows, just described, interferes seriously with this plan; the foul air coming in contact with these cold surfaces falls to be still more vitiated. A popular error is to confound cool air with fresh air. Unless the air is admitted by numerous openings it is not Draughts.-Persons exposed to out door in- supplied to all parts of the room, and especlemency, as sailors, soldiers on the march, cially stagnates in the corners. When large engineers, and sportsmen, seldom take cold. openings of egress are used, there is danger of The only precaution seems to be to avoid sit-downward draughts. The downward system is ting or lying on the bare ground, or checking much employed in large buildings. The fresh sweating by rapidly cooling off after violent air is admitted at or near the ceiling by numerexercise. It is when a portion only of the ous openings, and drawn off in the same way body is chilled that there is the most risk. A near the floor, the necessary draught being obman will escape harm from a ducking, but be tained by a chimney stack, in which is a fire, made sick from wet feet. The inmates of steam jet, or exhausting fan. This method houses are exposed to draughts, not only has given great satisfaction, and is now largely through cracks and key-holes, but from down- adopted in hospitals. The emanations from ward currents of cold air from within, due to each individual may be removed without havthe cooling effects of walls and windows. (1) ing opportunity to mingle with the general air Walls. The passage of the outer air through of the room.† walls has just been spoken of, and it need only be said that independent of this, the building material possesses a high radiating power, and the heat conducted through the wall rapidly passes into the outer space. A glance at a painted wall in a crowded church or lectureroom will show it to be coated with condensed moisture. The paint may be impervious, but does not prevent the cooling by conduction and radiation. Air cooled by contact with the wall falls, making a draught even in a close room. (2) Still more marked is this the case with glass. A window, as tight as art can make it, is cold to the touch in wintry weather, and soon is coated with moisture or frost. Although glass is impervious to air, yet its radiat-attendant a patient may be safely left, if well covered up. ing power is high (90 on Melloni's scale, the highest being 100), and from the thinness of the plates in windows it conducts rapidly. The outer surface is rapidly cooled by radiation and by contact of the outer cold air, and the inner surface soon acquires and maintains nearly the same temperature. Hence persons sitting by a closed window are exposed to downward

In a moderately well-built house, about twenty-five years old, the combined area of the cracks in a single room, with three windows and two doors, was found to be equal to a single opening of nearly one square foot of In a badly built house in an exposed situation the inflow through cracks was sufficient to prevent the warm air, from the heater in the cellar, from rising through the register until the draught was checked by the use of sand bags on the windward side of the house. B. H. R.

area.

In dwelling houses systematic ventilation is rarely found. A window lowered from the top, or a door ajar with a chain bolt, are the commonest methods. Sometimes ventilating

* One square foot of glass surface will cool over one cubic foot of air per minute from the temperature of the inner to that of the outer air. A single glass window, 6 by 3 feet (supposed to be air tight), will thus cool by contact 108 cubic feet per minute, when the outer air is at 0° the inner at 60°; a dead loss of fuel. This, if saved, would suffice to warm fresh air more than sufficient for ten persons, or to enable the windows of the room to be thrown wide open for fifteen minutes or half an hour. This is the best practical ventilation for a bedroom or sitting-room. It should be done while the room is not occupied, unless in the judgment of the medical

The remedy is to be found in hollow walls and double sashed windows. When double sashes are too costly double panes with an air space between are useful. When transparency is not essential, a tight fitting frame over which is stretched some translucent material, as oiled silk or waxed paper, does good service.

†The American Academy of Music is an example of a nearly perfect system of upward ventilation. The auditorium is separated from the outside walls by an inside lobby, so that there are no down currents of cooled foul air; each separate gas burner beneath the tier of seats, in all 205, has a ventilating register. A chandelier of 200 burners occupies the centre of the dome, over which is a large opening of exit. The draught of escaping heated air is powerful but not perceptible to the audience. Fresh air is supplied by grated openings in the floor, and a forcing fan, 10 feet in diameter, 120 revolutions a minute, is used at each performance. The seating capacity is 3000, and when crowded there is no offensive smell in the highest gallery, although the heat radiated from the chandelier is unpleasant.

registers furnished with a valve to prevent back | heat. After a meal some are chilly, others draughts and opened and closed by a cord are flushed. Hence, in a mixed assembly, there is fitted into the chimney. They are useful, but always complaint. After the large sums spent being usually placed over the hot air register in the ventilation of the English Houses of draw off the admitted air without giving it a Parliament and the Capitol at Washington, it chance to diffuse. With a door ajar the heated has in neither case given satisfaction. In a air passes out at the top, the outer air enters quiet sitting-room 65°-70° is generally agreenear the floor. The result is apt to be unpleas-able. In sleeping-rooms, the occupants being ant and hurtful draughts. With a window lowered at the top some fresh air enters at the lower edge of the opening, while the heated atmosphere escapes at the upper; some air also comes in by the space between the lower or fixed sash and the upper (lowered) frame. The sash blind being lowered, draughts are thereby mitigated. In any case where possible the ventilation should be in a communicating adjoining room, which will avoid the draught.

pending the cause, as yet unknown, of disease. We have also deodourisers, which have a limited use in disguising noxious odours. In all cases where possible the offensive matter must be removed by ventilation, thorough cleanliness, and other measures already mentioned.

5.86 grains of water to be added to maintain | tion, which favor the spread of diseases in some its moisture at that standard. This may be undetermined way. (2) By destroying or sussupplied artificially by an evaporator in front of the warm air register or on top of the stove. Those attached to cellar heaters, being left in the charge of servants, are rarely kept filled. Some moisture comes from the bodies of the inhabitants, steam from the kitchen and laundry, from plants kept in rooms and often watered, and a large proportion through walls. An ordinary brick will absorb of its weight of water walls exposed to the beating of storms become damp on the inside from the water soaking through. This is remedied by coating the wall with boards or tin, or by planting clinging vines against it. These ward off the rain, and by the absorbing power of their tendrils draw moisture from the porous wall. This is contrary to vulgar prejudice, but is true. Excessive dampness existing in rooms can only be remedied by raising the temperature.

The influence of moisture on the health is yet a matter of discussion. In the out-door air dampness produces languor in warm seasons, and chilliness in cold, independent of the state of the thermometer. A dry air at 95° with a breeze is more bearable than a saturated air at 80°. So a moist atmosphere at 40° is more trying than a still air at or some degrees below 。°. We find that people who inhabit climates where it rains almost every day, as in some parts of Scotland and Ireland, and those in rainless districts where the moisture cannot be detected by the hygrometer, enjoy good health under similar surroundings in other respects.

Even in houses we have men employed as shampooers in Russian and Turkish baths, in dye-houses, and other manufactories, living for several hours daily in a hot saturated atmos phere without injury. In artificially heated rooms the dried air causes discomfort, which cannot accord with good health. This is less marked when the heat is from steam or hot water circulating in wrought-iron pipes. The artificially dry air from stoves and heaters contains products of combustion which have escaped as before pointed out. This fact will, in part, account for the difference.

(1) The progress of decay requires the presence of air and moisture, with a temperature between the freezing and boiling points of water. Hence the known preservative effects of dry hot air, as seen in dried fruits and meats, and of those excluded from the air (canning). In polar climates flesh of animals has been preserved for centuries, and refrigerator cars and ships are used for transportation of fresh meats over thousand of miles.

A temperature of from 150° F. to 240° F. seems absolutely to disinfect clothing, dwellings, hospital wards, shipping, etc. It is supposed to act by destroying the unknown germs of contagion, infection, and miasm. A temperature below freezing suspends miasmatic poisons, as yellow fever, cholera, intermittents, etc., but cannot be said to destroy them.

The chemical disinfectants act by destroying organic matter whether fixed or aërial, by preventing decomposition and collaterally by removing offensive smells. The most important may be named, as follows: Creasote and the nearly identical carbolic acid, which coagulate albumen and destroy the low forms of organism (bacteria, vibrios, etc.), which, if not the cause of fermentation and putrefaction, accompany it. Being volatile, they also act on the contaminated air. Permanganate of potassa, potassium permanganate, KO, Mn,O, [K,Mn,O,] alone, or more rapidly on the addition of dilute mineral acids, gives off oxygen as ozone, and thus destroys both fixed and aërial organic matter. It is very efficient but somewhat costly, not so much so, however, as to interfere with its use in the ordinary household. rine and sulphurous acid (sulphur dioxide), the former obtained from ordinary chloride of lime mixed with water, or more rapidly by the addition of an acid, the latter by burning sulphur, are especially adapted to use in unfurnished and untenanted rooms. The walls and ceilings should be previously thoroughly scraped, and afterwards whitewashed. are irrespirable when concentrated, and injurious to furniture. Chlorinated soda (Labarraque's solution) is more permanent and manageable than the corresponding lime salt, and may be used in lotions, etc. They act by removing hydrogen. The sulphurous acid is Disinfectants.-These are supposed to act cheaper than Cl, and less destructive to metals (1) by preventing fermentation and putrefac-exposed to it. One pound and a half of sul

Dampness of cellars and houses, and between decks of ships, is known to develop scrofula, rheumatism, phthisis, and to promote the spread of contagious and epidemic diseases.

This has been accounted for by the supposition that the dampness favors the spread of the virus or assumed germs of disease, as it does the perfume of flowers, or the stench of drains. We really know little about it, except the facts stated.

Both gases

phur, burned with suitable precautions against | are seldom used. The so-called disinfectants fire, suffices for one thousand cubic feet of air, sold under proprietary names are costly and the windows and doors being kept closed. no better than those heretofore considered. Bromine and iodine are expensive and possess no advantage over potassium permanganate. Hyponitric acid, NO,, (nitrogen peroxide, N2 Q.) is a powerful oxidizing agent, but is not now much used. It is made by the action of strong nitric acid on copper turnings. It can not be used in furnished or inhabited rooms.

2

The market price, which fluctuates, may be given as follows for the crude products, which answer every purpose for ordinary use: Carbolic acid (commercial creasote), 70 cts. a lb. Permanganate of potassa, 80 cts. a lb. Chloride of lime, 5 cts. a lb. Labarraque's solution, 6 cts. a lb. Copperas, 5 cts. a lb. SulOf the non-volatile disinfectants may be men- phate of alumina, 25 cts. a lb. Sulphate of tioned ferrous sulphate, FeO,SO, [FeSO,], cop-copper, 9 cts. a lb. Corrosive sublimate, 60 peras, green vitriol. It is very cheap and efficient, and is one of the best materials (preferably mixed with its weight of lime) for deodourising privies and drains. It acts in two ways: (1) By absorbing sulphuretted hydrogen. (2) By oxidizing organic matter. The iron absorbs oxygen from the air, becoming sesquioxide, Fe,O,, which is reduced by the organic matter to the protoxide, FeO, the organic matter being partially consumed by the oxygen given off. The protoxide again absorbs oxygen from the air, and thus the process is continuous. This action is seen in ordinary iron mould, which if not removed is soon found to eat a hole through the fabric. The salt should be used freely.

Charcoal, in coarse powder, absorbs both fixed and volatile organic matter, and by its power of absorbing and condensing oxygen in its pores rapidly consumes it. It is used in respirators, on perforated trays in ventilators of sewers, foul wells, and earth closets. It should be dry and freshly burned. Dry earth acts like charcoal, and when containing clay by the alumina present. The earth closet has come largely into use where water closets are not attainable. It has given general satisfaction. Lime has been already alluded to. Freshly slaked it is caustic, and destroys organic matter. As whitewash it is invaluable. For sanitary purposes simple slaked lime should be

used.

cts. a lb. Nitrate of lead solution, 10 cts. a lb. Deodourisers.-These act by disguising offensive odours, and in some cases at the same time give off ozone, as tar fumigations, turpentine, eucalyptus, and some other volatile oils. In all cases their use is only to be recommended where cleanliness and ventilation have been thoroughly used. Pastilles of fragrant gums, candles of myrtle wax, fumes of burned sugar, of roasted coffee, of vinegar, camphor, etc., are familiar. They may act usefully, by preventing the disgust and nausea due to the bad smell, and morally by the reassurance afforded to the timid during epidemics by the belief in their virtue. The metallic salts generally absorb sulphuretted hydrogen, one of the constant constituents of offensive odours, and are thus useful as deodourisers.

DANGER OF COLD BATHING.

Dr. George Johnson, of Kings College, says (London Lancet): "From what I have seen of the effects of cold bathing, I have arrived at the conclusion that more people are injured than are benefited by the practice; and I am confident that, if the urine of all men, women, and children, who paddle about in the sea until they are blue and cold, were tested within a few hours after their immersion, it would be found to be more or less albuminous in a large proportion of cases." The same objection will hold good against the morning cold bath in the Alumina compounds (sulphate, chloride) are case of a majority of persons; only those of fixed, and not adapted to aërial poisons. Oth- vigorous constitution can practise it throughout erwise they act like creasote and carbolic acid the year with impunity. by coagulating putrescible matter, and are cheap should "avoid emulation," taking his morning The ordinary citizen and useful local applications. The sulphate in bath at a temperature that he finds by experi solution is valuable in cleansing the hands after ence will best agree with him, and from which post-mortem examinations or offensive surgical he promptly reacts. If the water produces operations. Both are themselves inodorous. chilly sensations, and reaction is imperfect, the Others of less importance may be named, sulphate of copper, chloride of zinc (Burnett's solution), used in embalming and in the preservation of timber; also corrosive sublimate, used for the same purposes. These act by their coagulating power. Nitrate of lead (Ledoyen's solution) is rather a deodouriser than a disinfectant. It is inodorous. Others not named

bath is doing harm instead of good. The best time in this latitude for sea bathing is in August and September, when the water is of higher temperature than the mean of the air.