her stars, she would not be beholden to any one, and was able to take care of herself." She said, "she thought the people were all a pack of fools to leave their houses; for her part, she did'nt believe the fever was in town at all." I thought how this sceptical old woman would change her tune, if she should be taken sick herself.

Having rested myself, and got a little camphor and hartshorn, I proceeded to the house where my friend lay ill. I met the Doctor at the door, who informed me that he thought his patient better; and asked me up to see him. On entering the sick chamber, the fiery red eye, the yellow skin, and peculiar, indescribable expression of countenance, immediately struck me as symptomatic of no ordinary degree of danger. I took him by the hand-it was burning hot. He watched my countenance with an expression of anxiety and apprehension, struggling with native firmness of mind. I tried to utter some words of consolation, but my manner belied my speech. He squeezed my hand in silence, and I left him, being unwilling to prolong a meeting which could only be painful to both. Poor fellow! I never saw him more, as he died within a few days afterwards.

I felt oppressed as I left the house, and directed my steps towards the Battery to get a little fresh air. This spot had been connected with some of my pleasantest associations, from my earliest childhood. Here, when scarcely emancipated from petticoats, had I sported and gambolled with my young companions. Here, on a holyday afternoon, had I flown my kite, and engaged in all the games and sports of the schoolboy. Often, too, in the bravery of boyhood, had I come down here in the depth of winter, to wade through the snow, or to engage in pitched battles of snow-balls, with the heroes of some rival school. And here, too, more recently, had I taken many a pleasant walk on a summer's morning, and inhaled the pure breezes that come sweeping up the bay, with health-imparting freshness, as if to greet the first appearance of the sun, on his rising. Every thing now seemed changed. The grass was parched up for want of moisture; the weather was close and sultry; and though thick clouds rolled over head, no rain ensued:-not a breath of air stirred. Every thing was calm, and still, and lifeless. It seemed like the awful pause preceding the shock of the earthquake. Not a living creature was to be seen; but far down the bay might be observed some little vessel rolling in the calm, with sails flapping, as if panting for breath. It appeared like the wild pageantry of some gloomy dream, in which a different aspect is given to well-known pla

ces; when the mind is filled with vague apprehensions of impending danger, and the soul utterly subdued by a deep and dreary sense of desolation. I felt sick at heart; and right glad was I to leave the spot, and retrace my steps homewards as fast as possible. By degrees I approached the busy haunts of men; and never did poor ghost experience more pleasure in "revisiting the glimpses of the moon," than did I at escaping from the poisonous air and gloomy scenery of the infected district

ON METEOROLOGY.

The atmosphere that surrounds the globe we inhabit, is the scene of numerous and important phenomena. With these our comfort and health is most intimately connected; and yet, although they take place in our immediate vicinity, and are continually producing marked effects upon our senses, we are much less acquainted with the laws that govern them, than we are with those that direct and regulate the motions of bodies situated at distances from us so remote as almost to baffle human conception. Yet this is not because a sufficient degree of attention is not paid to the changes that occur in the atmosphere; for they form an object of constant observation and remark to all classes of mankind; but our ignorance arises from the want of regular and correct registers of the more obvious appearances, and of instruments by which the more hidden phenomena may be discovered and observed. This last defect bids fair to be soon obviated. The labours of several powerful minds have of late years been devoted to the science of meteorology. Much has been thus accomplished in the discovery of causes that affect climate, and in the contrivance of instruments to observe and register them; but by far the most important work that has yet appeared on this subject is that of Daniell.* We shall endeavour to give our readers an analysis of this interesting volume.

The earth, as is well known, is surrounded by an atmosphere, whose principal constituent part is a permanently elastic fluid, that may, as far as its effects upon climate are concerned, be considered as homogeneous. The temperature of this, at any point of the earth's surface, may be observed by means of a thermometer, and its mechanical pressure by the barometer.

* Meteorological Essays and Observations, by J. F. Daniell, F. R. S. London, 1823. pp. 464.

These instruments are so familiar as to need no description; their use and construction are both well known to all persons pretending to the appellation of scientific. It may not, however, be irrelevant to remark, that no standard thermometer is known to exist; and that most barometers are carelessly made, and filled with mercury, from which the air has not been sufficiently extracted.

Were the earth a sphere of uniform temperature, and at rest in space;* its atmosphere a perfectly dry and permanently elastic fluid; the height of the latter would be constant over every point of the earth's surface, and its density and elasticity, at equal elevations, every where the same. The column of mercury that it would support in the barometer, would therefore be the same at every point on the surface of the sphere; and equal at equal heights above the surface. The atmosphere would be absolutely at rest; and as its elasticity is proportioned to the pressure, the density would decrease in geometrical progression, while the distance from the surface of the sphere increases in arithmetical. When air is rarified, its capacity for heat is increased, and vice versa ; the sensible heat of the atmosphere must, therefore, decrease as the altitude increases; and as this changes the volume of elastic fluids, even under equal pressures, the barometer alone will no longer be the exact measure of the progressive density, but must be associated with the thermometer. Any change of temperature that affects every part of the sphere, would cause an increase in the elasticity of the atmosphere, and in its consequent height, without producing any motion in the lateral direction, or any change in the pressure upon the surface; but the pressure will be changed at all other altitudes.

If the temperature of the sphere, instead of being equal at every point, were greatest at the equator, and decreased towards the poles, the pressure on every point of the surfacewould still continue the same; but the altitude of the atmospheric column would become greatest at the equator, and its specific gravity at the surface less there than at the poles. The heavier fluid at the poles must, by its mechanical action, press upon and displace the lighter, and a current will be established in the lower part of the atmosphere from the poles towards the equator. The difference in the specific gravity of the polar and equatorial columns becomes less as we ascend into the atmosphere; while the elasticity, which is constant at the surface, varies with the height, and the barometer stands

Essay 1st, part 1st.

higher at equal elevations in the equatorial than in the polar column. It will hence happen, that, at some definite height, the unequal density of the lower strata will be compensated; and a counter-current will take place in the higher regions from the equator towards the poles. Our author has investigated the height at which this would happen, under certain circumstances, and calculated the velocity of each current at different elevations. The velocity and direction of these currents may be affected by the partial rarefaction or condensation of any of the columns; and such change of density will naturally take place, in consequence of the vicissitudes of the seasons, and the alternations of day and night.

If the sphere be set in motion, and made to revolve around its polar diameter, as an axis, an apparent modification will take place in the direction of the currents. The lower current, coming from a point whose velocity of rotation is less than that at which it arrives, will appear to be affected with a motion, in a direction contrary to that of the revolution of the sphere; while the upper current, being under opposite circumstances, will be apparently affected in an opposite manner. Hence we find, in the equatorial regions of the earth, winds that blow continually from N. E. on the northern side of the equator, and from the S. E. on the southern. In this region, the temperature is subject to little variation, and the general causes that have been described are more powerful than the local action; but, as slight irregularities of temperature are capable of producing great disturbances, that would act unequally on the antagonist currents, accumulations in some parts, and consequent deficiencies would arise, and cause temporary and variable winds, that in the higher latitudes would modify the regular currents, and often reverse their courses.

The atmosphere is not composed entirely of a homogeneous and permanently elastic fluid, but always contains a considerable portion of aqueous matter. It has been supposed by some that this is chemically combined with the air; by others, that it exists there in the form of vapour. The experiments of Dalton have established, conclusively, that the latter is the true theory; and that every given portion of space is capable of containing, at a given temperature, a certain amount of aqueous vapour, whether there be air present or not. Mr. Daniell proceeds, in the second part of his first essay, to investigate the phenomena of an atmosphere composed entirely of aqueous vapour; and the third part treats of one composed of permanently elastic and condensable fluids mixed. It would occupy too much space to follow him in this most ingenious and inteVol. I. No. II.

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resting inquiry; we shall therefore content ourselves with stating, in his own language, the results at which he arrives.

"The specific gravity and elasticity of the air is but slightly affected by this intermixture of aqueous vapour; so slightly, indeed, that the course and velocity of the currents may be considered, without any chance of disturbing our main argument, as unaltered. It will also be remarked, that while the great aerial ocean is divided into two distinct strata, flowing in opposite directions from south to north, the aqueous part, which is nearly confined to the lower current, presses in a contrary direction. The adjustment of these particulars remaining as now supposed, the compensating winds flow on in the courses which have been described, and the balance remains undisturbed."

Although the general currents are so little affected by the mere presence of aqueous vapour, the variations of temperature that are produced by its evaporation and condensation will tend to produce changes in their direction; these will be of great importance, but modified by local circumstances. The surface of the earth is not uniformly composed of one substance, but is partly covered by land, and partly by water. The evaporation from surfaces of these two different natures will be very different, and the changes of temperature arising from this source must vary with every modification of local circumstances. The quantity of moisture, then, that the air of any particular place contains, will have an influence upon its climate; nor can any set of meteorological observations be complete, when this is not employed as an element. The increase of weight acquired by deliquescent salts, the tension of cords, the shortening of whalebone, hair, and of some vegetable substances, have all been applied to this purpose, but with little success. Aware of the great importance of this subject, Mr. Daniell has planned and constructed a hygrometer that must, when its merits shall be fairly appreciated, supersede all others. Hygrometers, constructed of the substances we have already mentioned, indicate merely the presence of different portions of vapour, without affording any means of determining its absolute quantity. Leslie has indeed proposed a modification of his differential thermometer as an hygrometer; and observations with this may be applied to the tables of vapour existing in space at a given temperature, as deduced from the experiments of Dalton; but his instrument, although beautiful and ingenious, in the highest degree, is liable to objections from which Mr. Daniell's is free. It requires abstruse calculations, and delicate corrections, on the nature of which philosophers are by no