The density and temperature of this fluid have also a tendency to decrease, as its distance from the surface augments by a rate less rapid than that of the former. Its equipoise would be maintained by the adaptation of the upper parts of the medium, in which it moves, to the progression of its temperature, and by a current flowing from the hotter parts of the globe to the colder. Constant evaporation on the line of greatest heat, and unceasing precipitation at every other situation, would be the necessary accompaniments of this balance. The conditions of these two states of equilibrium, to which, by the laws of hydrostatics each fluid must be perpetually pressing, are essentially opposed to each other. The vapour or condensible elastic fluid is forced to ascend in a medium, whose heat decreases much more rapidly than its own natural rate: and, it is consequently condensed and precipitated in the upper regions. Its latent caloric is evolved by the condensation, and communicated to the air; and it thus tends to equalize the temperature of the medium in which it moves, and to constrain it to its own law. This process, the author considers, must evidently disturb the equilibrium of the permanently elastic fluid, by interfering with that definite state of temperature and density which is essential to its maintenance. The system of currents is unequally affected by the unequal expansion, and the irregularity extended, by their influence, much beyond the sphere of the primary disturbance. The decrease of this elasticity above, is accompanied by an extremely important re-action upon the body of vapour itself, being compelled to accommodate itself to the circumstances of the medium in which it moves, its own law of density can only be maintained by a corresponding decrease of force below the point of condensation; so that the temperature of the air, at the surface of the globe is far from the term of saturation; and the current of vapour which moves from the hottest to the coldest points, penetrates from the equator to the poles, without producing that condensation in mass, which would otherwise cloud the whole depth of the atmosphere with precipitating moisture. The clouds are thereby confined to parallel horizontal planes, with intermediate, clear spaces, and thus arranged are presented to the influence of the sun, which dissipates their accumulation, and greatly extends the expansive power of the elastic vapour. The power of each fluid being in proportion to its elasticity, Mr. Daniell considers that of the vapour compared with the air can never exceed at most 1.30; so that the general character of the mixed atmosphere is derived from the latter, which in its irresistible motions must hurry the former along with it. The influence, however, of the vapour upon the air, though slower in its action, is sure in its effects, and the gradual and silent processes of evaporation and precipitation govern the boisterous power of the winds. By the irresistible force of expansion unequally applied, they give rise to undulations in the elastic fluid; the return

ing waves dissipate the local influence, and the accumulated effect is annihilated, again to be produced.

"In tracing the harmonious results of such discordant operations," eloquently observes our author, "it is impossible not to pause, to offer up a humble tribute of admiration of the designs of a beneficent Providence, thus imperfectly developed in a department of creation where they have been supposed to be the most obscure. By an invisible, but ever active agency, the waters of the deep are raised into the air, whence their distribution follows, as it were by measure and weight, in proportion to the beneficial effects which they are calculated to produce. By gradual, but almost insensible, expansions, the equipoised currents of the atmosphere are disturbed, the stormy winds arise, and the waves of the sea are lifted up; and that stagnation of air and water is prevented which would be fatal to animal existence. But the force which operates is calculated and proportioned the very agent which causes the disturbance bears with it its own check; and the storm, as it vents its force, is itself setting the bounds of its own fury. The complicated and beautiful contrivances by which the waters are collected "above the firmament,” and are at the same time "divided from the waters which are below the firmament," are inferior to none of those adaptations of INFINITE WISDOM, which are perpetually striking the inquiring mind, in the animal and vegetable kingdoms. Had it not been for this nice adjustment of conflicting elements, the clouds and concrete vapours of the sky would have reached from the surface of the earth to the remotest heavens; and the vivifying rays of the sun would never have been able to penetrate through the dense mists of perpetual precipitation."-P. 132.

The reference to this admirable and complicated agency by which the different constituents of the atmosphere are so beautifully and regularly balanced, leads the author to the consideration of a subject which has always been a favourite with the sceptic, and on which we must necessarily continue to remain in considerable doubt and conjecture: still, the philosophical explanation which Mr. Daniell adopts, along with Mr. Granville Penn, to whom he expresses himself indebted for the first idea of it, appears to us the most probable of any that has been propounded, and the most consistent with those principles which are known to regulate the aërial fluid.

"The question has been asked," says the author, "How is it that light is said to have been created on the first day, and day and night to have succeeded each other, when the sun has been described as not having been produced till the fourth day? The sceptic presumptuously replies, this is a palpable contradiction, and the history which propounds it must be false. But Moses records that God created on the first day the earth covered with water, and did

not till its second revolution upon its axis, call the firmament into existence. Now, one result of the previous inquiry has been, that a sphere unequally heated and covered with water, must be enveloped in an atmosphere of steam, which would necessarily be turbid in its whole depth with precipitating moisture. The exposure of such a sphere to the orb of day would produce illumination upon it, that dispersed and equal light, which now penetrates in a cloudy day, and which indeed is "good:" but the glorious source of light could not have been visible from its surface. On the second day the permanently-elastic firmament was produced, and we have seen that the natural consequences of this mixture of gaseous matter, with vapour, must have been, that the waters would begin to collect above the firmament, and divide themselves from the waters which were below the firmament. The clouds would thus be confined to definite plains of precipitation, and exposed to the influence of the winds, and still invisible sun. The gathering together of the waters on the third day, and the appearance of dry land, would present a greater heating surface, and a less surface of evaporation, and the atmosphere during this revolution would let fall its excess of condensed moisture: and, upon the fourth day it would appear probable, even to our short-sighted philosophy, that the sun would be enabled to dissipate the still-remaining mists, and burst forth with splendour upon the vegetating surface. So far, therefore, is it from being impossible that light should have appeared upon the earth before the appearance of the sun, that the present imperfect state of our knowledge will enable us to affirm, that, if the recorded order of creation be correct, the events must have exhibited themselves in the succession which is described. The argument, therefore, recoils with double force in favour of the inspiration of an account of natural phenomena, which in all probability, no human mind, in the state of knowledge at the time it was delivered, could have suggested; but which is found to be consistent with facts that a more advanced state of science and experience have brought to light." P. 134.

The important modifying influence exerted over atmospheric phenomena by the electric fluid and the moon, are not entirely passed over by our author in his interesting inquiry, although he has not been able to add any thing to our existing stock of knowledge on the subject from those experiments, however, instituted by him, he is inclined to believe that the elasticity of vapour is increased when electrically charged, but on this point he has nothing decisive to offer. The popular and general opinion of the different phases of the moon possessing an influence over atmospherical vicissitudes which has been denied by some philosophers, and considered as the offspring of superstition and ignorance, is attentively considered by the author, and accorded with. Innumerable observations have shewn that such a relationship does actually exist, and it is not at all more extraordinary than the influence exerted over the tides by that satellite.

Of the next essay, "On the Construction and Uses of a New Hygrometer," we shall say but little; the ingenious ideas which led to its adoption: its mechanism and uses have been already detailed in this Journal, by the author, and the practical observations made with it in different portions of the globe, communicated by different scientific individuals through the same channel. To those, however, who have not perused Mr. Daniell's description of the instrument, the essay before us will afford every necessary information regarding its construction, and mode of employment.

The author complains, and not without justice, of the difficulties experienced in "approaching the shrines whence the oracles of science are issued," and relates the following anecdote which we wish were unique: unfortunately, it is not the first instance by many where obstructions have been experienced in the fair investigation of philosophical discoveries by the academy in question, and frequently, we fear, from an overweening desire to promulgate the discoveries of their countrymen, and a corresponding apathy towards those of other nations.

"Being actuated," says Mr. Daniell, "by the wish to obtain contemporaneous observations, and to do all in my power to facilitate so desirable an object, and my own opinion being confirmed by those whose judgment I could not doubt, I took an opportunity of sending by a private hand, two of the hygrometers, in their most perfect state, to one of the philosophers of the French Royal Academy of Sciences, the most distinguished for chemical knowledge and discoveries. I requested his opinion of the merits of the instrument, and authorized him to present one of them, in the most respectful way to the Academy. My presumption has, I suppose, been roperly checked, by no notice whatever having been taken of what was certainly meant as a mark of humble respect, either by the individual, or the learned body: to the former of whom, having had the advantage of a personal introduction, I cannot feel that I have been to blame in addressing myself, however small may have been my pretensions for obtruding myself upon the latter." P. 185.

The next essay to which we shall advert, comprises a dissertation on the climate of London; a subject not less interesting to the lover of meteorology as a science, than to the physician; there are, however, so many circumstances independently of the exact condition of the atmosphere as regards temperature and dryness, which exert a baneful influence over human health, that these phenomena are not so decisive in the study of causation as might à priori be imagined: it has indeed been asserted by some philosophers that the greater salubrity of one country over another is principally owing to the lesser degree of noxious emanations from its soil; and Heberden, Blane, and others, have affirmed that on the whole, except in the case of extraordinarily cold winters, the fluctuations of the weather in this climate do not much affect health. Still epidemics do occur,

which there is every reason to suppose have been occasioned by atmospherical changes, and consequently, as we have observed in a former part of this article, if these variations, barometrical, thermometrical, and hygrometrical, were carefully and regularly arranged at corresponding periods, and the changes in the condition of public health accurately marked, some very interesting and valuable information might in all probability be obtained, not less important to the physician than to mankind in general.

We can only enumerate here these general characters of the climate as adduced by Mr. Daniell, on an average of three successive years. The monthly phenomena are given, accompanied with popular observations on the corresponding conditions of the weather, the state of vegetation, health, &c.: but for those we must refer the reader who may be anxious to peruse them, to the work itself.

The observations were made three times a day, viz., from eight to ten o'clock A. M., from half past three to half past five P. M., and from ten to half past eleven P. M.

The mean pressure of the total atmosphere as denoted by the barometer was found to be 29.881 inches: the mean of twenty years, deduced by Mr. Howard from the observations of the Royal Society being 29.8655 inches. The mean temperature derived from the daily maxima and minima of the thermometer was 49°.5, corresponding even to the decimal place with Mr. Howard's estimate. The mean dew-point was 440.5, as also calculated from the daily maxima and minima. The elastic force of the vapour was consequently 0.334 inch, and a cubic foot of the air contained 3.789 grains of moisture. The degree of moisture was represented by 5° upon the thermometric scale, and the degree of moisture by 850 upon the hygrometric. The average quantity of rain was 22.199 inches, and the amount of evaporation calculated from the hygrometer, 23.974 inches; and the weight of water, raised from a circular surface of six inches diameter, 0.31 grains per minute.

The Barometric range was from 30.82 inches to 28.12 inches: the range of the dew-point from 70° to 11°. The pressure of the vapour varying with it from 0.770 inch, to 0.103 inch. The maximum temperature of the air was 90°, the minimum 11°. The force of radiation from the sun averaged 23°.3 in the day, and that from the earth at night 4°.6: the highest temperature of the sun's rays was 154°, and the lowest temperature on the surface of the earth 5°. The greatest degree of dryness was 29°, or the least degree of moisture upon the hygrometric scale 389. The time of the day was found, in some degree, to influence the near results; and one of the most constant effects was that produced upon the barometer. The mercurial column reached its greatest height in the morning, declined to its lowest in the afternoon, and again rose at night. The average difference of these periods, as exhibited by the journal, was as follows:-Morning above night +.005 inch; afternoon below morning -.015 inch;