may acquire a temperature of 70° or 80° before it reaches the head; and Dr. Reid has often noticed a difference of 11° and 12° in winter between the temperature of the floor of the lower deck of a man-of-war, where the air was permitted to enter, and that of the atmosphere about five feet above on the same deck, where the hammocks were slung. Even in a dense crowd in the open air, on a dull or calm day, when no current of air is produced by the sun's rays, the atmosphere becomes perceptibly offensive and impure.

Upon the effects of a free or restricted supply of air upon the appetite for food, &c. Dr. Reid thus observes :

"It appears to be universally admitted, that a low diet diminishes the necessity for much air, and that, on the other hand, where there is little air, there cannot be a great appetite for food. There are no periods accordingly, if we except a period of severe bodily exercise, where the constitution demands such a variety of supply as immediately before and after dinner; and, in the present state of society, a large share of the evil not unfrequently attendant upon a dinner party, does not always arise so much from individuals having taken more than their constitution requires, but rather from the vitiated air with which the system is usually surrounded at such periods.'

In illustration of this opinion a circumstance is related of a large party of Edinburgh philosophers being enabled to unconsciously consume many times more than their ordinary complement of wine, without any immediate or ultimate ill-effects, in consequence of the dinner being given in a properly-ventilated saloon. So, too, it is said, men have struck for wages in those manufactories where efficient ventilation has been established, in consequence of being unable to obtain the additional amount of food their improved appetites demanded. If this be not an exaggeration we fear it offers little encouragement to augment the means of ventilation in the abodes, &c. of the humbler classes. People who have the greatest difficulty in obtaining the wherewith to satisfy the cravings of hunger already, have little need of the additional torture of a keener appetite. Indeed, in another part of his work, the author allows that fresh air must not be too freely introduced into the abode of misery, as there are other still more pressing and incompatible wants.

"Ventilation need not be expected where food, fuel, and clothing are deficient. Heat is still more essential to the human frame than fresh air, which consumes the body by slow combustion or oxygenation, when food is not supplied. Defective ventilation reduces the oxygenation, preserves warmth, stupifies the feelings, and allays the pangs of hunger. By reducing the power of oxygenating the blood, and of sustaining the temperature, it produces a condition which diminishes the relish and power of digesting plain and wholesome food. Unnatural stimuli, such as ardent spirits and opium, are required to excite the languid circulation, and make it feel, though only temporarily, that vigour of circulation which gives animation and vivacity to the intellect, as well as strength to the body. The actual state of the atmosphere, in the habitations of the extremely poor, is too bad and too revolting to be understood by any except those who actually visit them. There are unquestionably many exceptions, but in general, external cleansing, and an improved condition in their means and habits are essential, before any decided improvements can be extensively introduced. If draughts and currents are offensive to all, there are few who are more sensitively alive to them than those whose hunger, want of clothing, and want of fuel, reduces them to the lowest scale of misery." 40.

However unavoidable this may be with the destitute, there is another class of the community who turn foul air into current coin.

"Nowhere is the operation of a vitiated atmosphere seen more distinctly than in numbers of the refreshment-rooms in which this great metropolis abounds. Many a hard-worked clerk too often imagines he has had enough for his support, because he has taken all that his appetite permitted; whereas the saturated atmosphere in which he dines may have reduced his appetite by a half, and made him contented with an inadequate supply. The profits in numerous such rooms, would diminish largely were they well ventilated, and were the appetite equally satisfied at the same time. But the subject is as yet very imperfectly known, and escapes, in a great measure, at present, the attention of both parties. Unquestionably, however, the landlord or proprietor of ill-ventilated refreshment-rooms has no right to charge at the same rate as those that have their apartments well ventilated." 182.

Speaking from former experience, we are inclined to think that the amount of food taken by the frequenters of the metropolitan eating-houses is amply sufficient for the inhabitants of cities, leading, as they for the most part do, comparatively sedentary lives; and as to the price, it seems surprising how so substantial a meal of good wholesome food can be furnished at so low a cost. We do not deny that a complete ventilation might much increase the appetite and the quantity of food taken, and the extent to which these both occur in the purer air of the country may be adduced; but we believe that, except among the poorest classes, the inhabitants of large towns already consume larger quantities of food than the demands made upon their system by habits of activity justify.

The air may be contaminated by various sources of impurity, especially in large cities, where these so extensively prevail; but the principal one and that which most have to contend against is the spoiling it by substituting carbonic acid gas for the oxygen removed in respiration, combustion, &c. &c. This substance, existing in the atmosphere as one part in two thousand is not to be looked upon in the light of an impurity, sufficing then only for the due supply of carbon to the vegetable kingdom. It is rare, however, to meet with air of this purity in dwelling-houses, and a far larger proportion is borne even with impunity. This has its limits.

"Some individuals work habitually in mines and other places, where from one to two per cent. and perhaps still larger quantities of carbonic acid are present. But death has ensued, in some peculiar cases, it is affirmed, where there was only one per cent. Any ordinary atmosphere containing one per cent. of carbonic acid must be regarded of very inferior quality, and not fit to sustain health, though in numerous apartments a much more vitiated air may be observed. Air containing 10 per cent. of carbonic acid, and other impurities of less note, a considerable amount of moisture, and at the same time a high temperature, constituted the most impure atmosphere charged with carbonic acid to which I have been exposed; nor am I aware that I could have resisted its action for any considerable period, had its influence not been gradually developed, as the pure air in which the experiment began had successive quantities of carbonic acid communicated to it.

"When carbonic acid is present in smaller proportion than is necessary to produce an immediate and overwhelming effect, it induces a trifling headache or intolerable oppression in endless gradations, according to constitutional peculiarities, and different circumstances connected with the state of the atmosphere in which it acts."

200.

It is an error to suppose that carbonic acid gas, by reason of its greater specific gravity, is found at the lower part of an apartment or locality in which it is generated. It is only when in large quantities and in a concentrated state that it descends like water, and accumulates in cavities on the surface of the ground. It is thus found in large graves, in old wells and pits, in brewers' vats, in the Grotte del Cane, &c.; but by reason of the property of diffusion which gases of different specific gravities, brought in contact with each other, possess, no gas, however heavy, remains for any length of time at the surface of the earth, and thus carbonic acid gas has been found at the highest altitude yet reached by man. The superior heated or rarified condition of respired or burned air causes it to ascend to the highest point in the apartment which is accessible to it, and thus it is at the upper parts of rooms, &c. and not below, where the fresh air enters, that the greatest amount of impurity exists.

If the apartments of private houses are insufficiently ventilated, public buildings, in which large numbers of persons occasionally assemble, are notoriously so. The supply of pure and the removal of vitiated air has hitherto formed no part of the architect's study; and, now that public attention has become roused to the necessity of this, alterations in buildings have to be effected at a great cost and in an imperfect manner, to produce the same effect which might have been provided for in the original construction of the building at little or no additional expense. The author signalizes churches as the buildings par excellence defective in ventilation, many of these containing no provisions whatever for change of air, although much crowded, and in the evenings adding to the impurities and consumption of oxygen by powerful illumination.

"In those churches in which I have watched the progress of vitiated air, as the service proceeded, on individuals whose constitutions were not previously rendered dead to the influence of pure air by the atmosphere they were accustomed to at home, a slight and marked flush in the countenance usually appeared in a short time this was soon succeeded by a sense of heat and oppression, and a tendency to sleep, more or less marked according to the condition of the atmosphere, and the extent to which the attention was engaged. The soporific influence was in some cases a source of annoyance to the conclusion of the service, but was succeeded in others by a re-action. The vis medicatrix naturæ did not remain inactive. The pulse rose, the circulation was accelerated, the brain became stimulated, and relief was at the same time afforded by the insensible perspiration (which had been arrested by the state of the air) becoming gross and sensible. Attention could now be sustained, but headach more or less severe was the usual consequence, and liability to dangerous colds and rheumatisms, where the body was suddenly exposed to the chilling influence of the external atmosphere, while still affected in the manner described."

These ill effects were always found, in a long series of examinations, most considerable where the proportion of carbonic acid gas was greatest. No means moreover are adopted to ventilate the church from week to week, or between the services, so that the congregation of the later part of the day is breathing the foul air vitiated by that which preceded them; and those of them who sit in the galleries receive only the air already contaminated in the area.

Schools, again, of both rich and poor, but of course especially of the latter, are lamentably ill supplied with air, which must powerfully contribute

to the production of ill-health among the young, who so particularly, during the condition of growth, require an efficient oxygenation of the blood.

To secure due ventilation it would seem to be sufficient to provide means for the escape of air as fast as it is vitiated, the means of ingress being usually sufficiently abundant in ordinarily-constructed abodes to allow a sufficiency to enter to supply the place of that which is removed. In this way a continued movement of the air is produced, without which no ventilation can ensue. The slightest elevations of temperature are sufficient to induce such movement, by rarifying and causing the ascent of the air nearest the heated body, the colder surrounding air rushing in to supply the vacuum thus formed. The atmosphere at a mean temperature and not agitated by wind, is warmed and expanded in this way (to about five degrees) on coming in contact with the human frame, and thus a current of air is constantly passing around it. The law of this motion of the atmosphere is thus stated. "The expanded warm air being always pressed upwards by any colder and denser air, and the movement being more or less rapid, according to the difference of temperature and amount of expansion between the air that is heated and the cold air in contact with it." Ventilation, however, at most seasons of the year by no means consists in the simple admission of the external air, and expulsion of that which is vitiated. At all periods, the latter should be provided for, but the difficulty consists in the colder portions of the year as to the admission of the former-a due supply of warmth being as essential to health and comfort as a due supply of air. Numerous have been the attempts to combine the effectual warming and ventilation of apartments, but the success which has attended them has been by no means commensurate with the attention bestowed and expense incurred.

The ventilation and warming of an ordinary English apartment by means of the grate and open chimney has been condemned by all as ineffectual, partial, and expensive; and those who have suffered from the inequalities of temperature, the currents of air, and the long coal- merchant's bills incidental thereto, must acknowledge that the objectors have reason on their side. It is familiarly known that, while a person seated near a good fire is suffering from an excess of heat reflected upon his person in one direction, he is subjected to the impinging in another of currents perhaps ten or twenty or more degrees too cold: and that, while one individual a few feet from the fire place may be comfortably warm only, another as many yards may be suffering from cold. The large proportion of the heat generated which is wasted in passing up the chimney needs no demonstration. With this loss of caloric even ventilation is imperfectly attained. The heat of the fire it is true determines the upward movement of the air in contact with it, whose place is supplied by other portions, and the motion so produced causes a certain amount of ventilation. But the air which has been vitiated rises by its lesser specific gravity to the upper parts of the room, and as the aperture into the chimney is placed much below, it cannot penetrate downwards through the mass of colder, denser air which has entered by the doors, windows, &c., and much of which passes out, little changed from when it entered, and much less requiring renewal than the stratum at the upper part of the room. Still, with all the imper

fections of this mode of warming and ventilating ordinary rooms, it is the best that has been yet devised for common use; and with the alterations of making a communication from the upper part of the room into the flue, so as to admit of the removal of the light vitiated air, and of rendering the aperture of the chimney below as small as possible, as indeed is done by the register stoves, so as to prevent the needless expenditure of heat, is not likely to be improved upon.

The advocates for the use of the varieties of stoves, as many of the German, Russian, and our own recent modifications, triumphantly point to the equability of temperature obtainable by the agency of these instruments, and the very small expenditure of fuel they produce. Sir George LEFEVRE, in the pamphlet indicated at the head of this article, attributes the great prevalence of phthisis in this country, and the comparative immunity enjoyed by Russia from this disease, to the greater care taken in the latter country to prevent inequalities of temperature by equably warmed rooms and appropriate clothing. He dwells with great force upon the comfortable condition of the interior of a Russian house even in the coldest weather, and contrasts this with the comfortless state of most English houses during Winters of infinitely less severity, both as regards the inequality of warmth and abundant currents of air in any one apartment, and in the contrast offered by the temperature of the different ones, especially the bed-rooms, which in the Russian houses are, like indeed every part of the mansion, completely warmed.

"I have been confined to my room," he says, writing to a friend in Russia, "by an obstinate cough, to which I was always subject in the Winter season while residing in England, but which I escaped during the whole time of my residence in St. Petersburgh. I had no idea I should suffer so much from the cold, yet it is not from external cold, for I took the precaution of bringing my Russian furs with me. This was quite unnecessary; for, after all the trouble I had with them, I find that I cannot wear them here. I do not understand the reason of this apparent anomaly, for I have a thermometer in my window, and find that the same degree of cold here is much more supportable than in St. Petersburgh. I should not have dared to have ventured out without a pelisse in Russia, where I find a P. jacket quite sufficient here to keep me warm. certain that eight degrees Reaumur in London, are more supportable than two degrees in the imperial city. It is, however, of the indoor cold that I have to complain so bitterly, for indoor warmth is a phenomenon only to be found in such houses as are provided with stoves in the ante-room, and double windows, of which comforts, alas! I have had no experience since I left Russia.

*

It is

"I am afraid you will be hardly able to read this scrawl, for I am writing to you in my bed-room, which is about the same temperature as your ice-cellars. The water is literally frozen in the jug, and I cannot see out of my windows, which are like ground-glass. It is enough to try one's temper to hear, as I do, when I complain of cold, that it is not so cold as in Russia' that surely I ought to bear the cold better here than those who have never been exposed to severe cold.' When I come down to breakfast, with blue hands and swollen fingers, I am offered the slop-basin to dip them in. I limp as I walk-You have chilblains, I suppose; they are common Winter guests; how dreadfully you must suffer from them in Russia!' Yet I never heard of them, or certainly never suffered from them, during ten years that I sojourned there. "What are most annoying to me are, the constant drafts which prevail in English houses. Every gust of wind makes the casements rattle, and if the