of every part, the noxious principle is conveyed to the lungs; where it is of necessity brought, if not actually, yet virtually, into contact with the air; and thus it is effectually removed from the system.

SECT. IX.

Effects of the Motion of the Air, as connected with
Human Health, &c.

In the history of water we had an opportunity of observing how extensive are the benefits arising to mankind from that physical property, by which its particles are capable of moving with the greatest ease among each other: nor are the benefits less considerable, which arise from the same property in the element now under consideration; especially when aided by those alterations in its volume, which follow upon every change of temperature: for from these combined causes arise those currents of air, which administer, in various modes, as well to the luxury and comforts of man, as to his most important wants.

Who does not see the miseries that would result from a stagnant atmosphere? To the houseless and half-clothed mendicant indeed, who under exposure to a wintry sky instinctively collects his limbs into an attitude as fixed as marble, lest by their motion he should dissipate the stratum of warmer air immediately surround

ing his body—to such an individual indeed, under such circumstances, a stagnant atmosphere becomes a benefit of the highest value; not only by preventing or moderating the painful sensation of cold; but by preventing the dissipation of that degree of heat which is necessary for the preservation of the vital principle, which in his unsheltered state might otherwise possibly be soon extinguished. But let circumstances be reversed: and, instead of the wretched beggar exposed to an inclement sky, let us picture to ourselves an Asiatic prince surrounded by all the luxuries which power and opulence can procure, but oppressed by the sultry atmosphere of a burning sun; how grateful to his feelings is the refreshing coolness occasioned by the artificial agitation of the surrounding air: in order to extend the means of obtaining which gratification, fountains of water are customarily introduced into the interior rooms of Indian and Arabian palaces, the evaporation of the spray of which gives a refreshing coolness to the air. Or let us recur to scenes more familiar, and more illustrative of the effect produced; to the bedside of the almost exhausted invalid, whose existence is alone made tolerable by the assiduous supply of fresh streams of air: there let us witness, in the thankful smile which animates his pallid countenance, the soothing sensation which the languid sufferer experiences. Even

for such a momentary solace, what, of all his most valuable possessions, would not every one of those miserable victims have surrendered, who once perished in that dreadful dungeon of Calcutta?

In many instances nature tempers the high degree of heat belonging to particular climates, by the periodical recurrence of cooling winds at stated hours of the day. Thus, in the islands and on the coasts in general of the tropical regions of the earth, the alternations of what are called the sea and the land breeze are of the highest importance to the comfort and health of the inhabitants of which the following statement, taken from an official paper on the medical topography of Malacca, furnishes a sufficient illustration". "The Malay peninsula possesses, though within the tropics, and almost under "the equator, a very equable temperature and mild climate. Whatever be the prevailing wind, the sea-breeze generally sets in from "the south between ten and twelve in the morning, and continues till six or seven in the even

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ing; when, after a short calm, the land wind 'begins to blow from the north-east and so "constant are these breezes, that, unless during a storm, the influence of the monsoon is scarcely perceptible. And so uniform is their

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m Printed at the government press, Pinang, 1830. See the Edin. Med. and Surg. Journal, for July 1831, p. 179.

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effect, with respect to the temperature of the air, that, throughout the year, the variation "does not exceed fourteen or fifteen degrees of "Fahrenheit; being rarely higher than eightyeight degrees, or lower than seventy-four de66 grees.

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And though the hurricanes, to which these regions are frequently exposed, are occasionally most dreadful in their effects upon the property and even the lives of the inhabitants; yet we may not only be assured on general principles of reasoning that in the main they are beneficial, but on some occasions we have immediate demonstration of their remedying a greater evil. Thus when swarms of a peculiar species of ant had, during many years, ravaged the island of Grenada, to so serious an extent that a reward of twenty thousand pounds had been offered to any one who should discover a practicable method of destroying them; and when neither poison nor fire had effected more than a partial and temporary destruction of them, they were at once swept away by a hurricane and its accompanying torrents of rain. Of the numbers in which these insects occurred, some estimate may be formed from the following statement of an eyewitness of credible authority; who says "he had seen the roads coloured by them for many miles together; and so crowded were they in many places, that the print of the

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"horse's feet was in a moment filled up by the

We who rarely are oppressed, for more than a few hours in a whole summer, by such a state of the atmosphere as occasionally precedes a thunderstorm, when no friendly breeze interposes to remove the close and humid stratum of air which envelopes our bodies, may well be thankful that our lot has not been cast in certain regions of the earth; in those Alpine valleys, for instance, whose scarcely human inhabitants attest the dreadful consequences of a confined atmosphere: the influence of which often affects not only the present sensations and comforts, but even the intellectual, and eventually the moral character, of those who are habitually exposed to it.

It appears, from recent inquiries, that the physical and intellectual and moral degradation, so often observable in the inhabitants of mountain valleys in general, but noticed particularly in the valleys of the Rhone, may be referred with probability, among other causes, to a stagnant atmosphere; and to the reverberation of heat from the sides of the mountains which bound those valleys, cooperating with an alternation of piercing winds: the degree of that degradation at least is always proportional to the action of those causes.

n Philos. Trans. 1790, p. 347.