XIX. ON VENTILATION.

[Abridged from the same.]

We are all thoroughly aware of the necessity of breathing; and the agreeable freshness and reviving influence of the pure morning air must convince us that the breathing a pure atmosphere is conducive to health; yet we as carefully exclude the air from our houses as if its approach were noxious. Intending to shut out the inclemencies of the weather only, in our care to guard ourselves from the external air, we hinder that renewal of the atmosphere which is necessary to prevent its becoming stagnant and unfit to support animal life.

Few persons are aware how very necessary a thorough ventilation is to the preservation of health. We preserve life without food for a considerable time, but keep us without air for a very few minutes and we cease to exist. It is not enough that we have air, we must have fresh air; for the principle by which life is supported is taken from the air during the act of breathing. One fourth only of the atmosphere is capable of supporting life; the remainder serves to dilute the pure vital air, and render it more fit to be respired. A full grown man takes into his lungs nearly a pint of air each time he breathes; and when at rest, he makes about twenty inspirations in a minute. In the lungs, by an appropriate apparatus, the air is exposed to the action of the blood, which changes its purer part, the vital air, (oxigen gas,) into fixed air, (carbonic acid gas,) which is not only unfit to support animal life, but is absolutely destructive of it. An admirable provision of the great Author of nature is here visible, to prevent this exhausted and now poisonous air from being breathed a second time;— while in the lungs, the air receives so much heat as makes it specifically lighter than the pure atmosphere; it consequently rises above our heads during the short pause between throwing out the breath and drawing it in again, and thus secures to us a pure draught. By the care we take to shut out the external air from our houses, we prevent the escape of the deteriorated air and condemn ourselves to breathe again and again the same contaminated, unrefreshing atmosphere.

Who that has ever felt the refreshing effects of the morning air can wonder at the lassitude and disease that follow the continued breathing of the pestiferous atmosphere of crowded or ill-ventilated apartments? It is only necessary to observe the

countenance of those who inhabit close rooms and houses, the squalid hue of their skins, their sunken eyes, and their languid movements, to be sensible of the bad effects of shutting out the external air.

Besides the contamination of the air from being breathed, there are other matters which tend to depreciate its purity; these are the effluvia constantly passing off from the surface of animal bodies, and the combustion of candles and other burning substances. On going into a bed-room in a morning, soon after the occupant has left his bed, though he be in perfect health and habitually cleanly in his person, the sense of smelling never fails to be offended with the odor of animal effluvia with which the atmosphere is charged. There is another case, perhaps, still more striking, when a person fresh from the morning air enters a coach in which several persons have been close-stewed during a long night. He who has once made the experiment will never voluntarily repeat it. The simple expedient for keeping down both windows but a single half-inch would prevent many of the colds, and even fevers, which this injurious mode of travelling often produces. If, under such circumstances, the air is vitiated, how much more injuriously must its quality be depreciated when several persons are confined to one room, where there is an utter neglect of cleanliness; in which cooking, washing, and all other domestic affairs are necessarily performed; where the windows are immoveable, and the door is never opened but while some one is passing through it!

It may be taken as a wholesome general rule, that whatever produces a disagreeable impression on the sense of smelling is unfavorable to health. That sense was doubtless intended to guard us against the dangers to which we are liable from vitiation of the atmosphere. If we have, by the same means, a high sense of gratification from other objects, it ought to excite our admiration of the beneficence of the Deity in thus making our senses serve the double purpose of affording us pleasure and security; for the latter end might just as effectually have been answered by our being only susceptible of painful impressions.

To keep the atmosphere of our houses free from contamination, it is not sufficient that we secure a frequent renewal of the air-all matters which can injure its purity must be carefully removed.

Flowers in water and living plants in pots greatly injure the purity of the air during the night, by giving out large quantities of an air (carbonic acid) similar to that which is separated

from the lungs by breathing, which, as before stated, is highly noxious. On this account they never should be kept in bedrooms; there are instances of persons, who have incautiously gone to sleep in a close room in which there has been a large growing plant, having been found dead in the morning, as effectually suffocated as if there had been a charcoal stove in the room.

A constant renewal of the air is absolutely necessary to its purity; for in all situations it is suffering either by its vital part being absorbed, or by impure vapors being disengaged and dispersed through it. Ventilation, therefore, resolves itself into the securing a constant supply of fresh air.

In the construction of houses, this great object has been too generally overlooked, when, by a little contrivance in the arrangement of windows and doors, a current of air might, at any time, be made to pervade every room of a house of any dimensions. Rooms cannot be well ventilated that have no outlet for the air; for this reason there should be a chimney to every apartment. The windows should be capable of being opened, and they should, if possible, be situated on the side of the room opposite to, and furthest from, the fire-place, that the air may traverse the whole space of the apartment in its way to the chimney. Fire-places in bed-rooms should not be stopped up with chimney-boards. The windows should be thrown open for some hours every day, to carry off the animal effluvia which are necessarily separating from the bed-clothes, and which should be assisted in their escape by the bed being shaken up, and the clothes spread abroad, in which state they should remain as long as possible; this is the reverse of the usual practice of making the bed, as it is called, in the morning and tucking it up close, as if with the determination of preventing any purification from taking place. Attention to this direction, with regard to airing the bed-clothes and bed after being slept in, is of the greatest importance to persons of weak health. Instances have been known in which restlessness and an inability to find refreshment from sleep would come on in such individuals when the linen of their beds had been unchanged for eight or ten days. In one case of a gentleman of a very irritable habit, who suffered from excessive perspiration during the night, and who had taken much medicine without relief, he observed that, for two or three nights after he had fresh sheets put upon his bed, he had no sweating; and that, after that time, he never awoke, but that he was literally swimming, and

that the sweats seemed to increase with the length of time he slept in the same sheets.

Various means are had recourse to at times, with the intention of correcting disagreeable smells, and of purifying the air of sick-rooms. Diffusing the vapor of vinegar through the air, by plunging a hot poker into a vessel containing it; burning aromatic vegetables, smoking tobacco, and exploding gunpowder, are the means usually employed. All these are useless. The explosion of gunpowder may, indeed, do something, by displacing the air within the reach of its influence; but then, unfortunately, an air is produced by its combustion, that is as offensive, and equally unfit to support life as any air it can be used to remove. These expedients only serve to disguise the really offensive condition of the atmosphere. The only certain means of purifying the air of a chamber which is actually occupied by a sick person, is by changing it in such a manner that the patient shall not be directly exposed to the draughts or cur

rents.

No fumigation will be of any avail in purifying stagnant air, or air that has been breathed till it has been deprived of its vital part; such air must be driven out, when its place should be immediately supplied by the fresh, pure atmosphere. The readiest means of changing the air of an apartment is, by lighting a fire in it, and then throwing open the door and windows; this will set the air in motion, by establishing a current up the chimney. The air which has been altered by being breathed is essential to vegetable life; and plants, aided by the rays of the sun, have the power to absorb it, while they themselves at the same time give out pure vital air. This process, going on by day, the reverse of that described before as taking place during the night, is continually in operation, so that the purification of the atmosphere can only be prevented by its being preserved in a stagnant state.

PART IV.

STATISTICAL AND GENERAL INFORMATION CONCERNING FOREIGN COUNTRIES.

XX. STATISTICS.

THE word Statistics is of modern origin, and denotes a detailed view of the population, industry, agriculture, and commerce of a country, or an inventory of its resources, force, revenues, and productions of every description. Something similar to this was practised in ancient times; for Aristotle, Xenophon, and other writers speak of periodical returns in Greece, bearing a resemblance to the statistics of the present day. It was also a custom sometimes to engrave important facts of this kind on walls and pillars. Tacitus tells us, that when Germanicus visited Thebes, he saw an inscription, which a priest interpreted to him as containing an account of" the tribute paid by the conquered nations, the specific weight of gold and silver, the quantity of arms, the number of horses, the offerings of ivory and rich perfumes presented to the temples of Egypt, the measure of grain and the various supplies administered by every nation, making altogether a prodigious revenue." He tells us, moreover, that Nero, when the people complained of the oppressions practised upon them by the collectors, issued a proclamation,"directing that the revenue laws, till that time kept among the mysteries of state, should be drawn up in form, and entered on the public tables for the inspection of all degrees and ranks of men." The Romans, for some time, were also in the habit of making periodical enumerations of the people. In these registers were noted the name, age, and year of birth, the sex, the number of slaves and of domestic animals, and a valuation of all the property. In many nations of the East, a similar usage has prevailed from time immemorial.

But the subject of statistics, as a science, is of recent origin. Achenwall, a professor of Göttingen University, was its founder, about the middle of the last century. In 1748 he pub