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1817.] which this article embraces. An account is given of the invention of the air pump, by Güricke of Magdeburg, about the middle of the seventeenth century,—of his statical balance and anemoscope: the introduction of experimental science into England, and the institution of the Royal Society, are next related; this naturally leads to the mention of some of its most celebrated members, as Boyle and Hook, the latter of whom greatly improved the form of the air pump; next come the experiments of Huygens, who, from the suspension of mercury in a glass tube exhausted of air, was led to infer the existence of a more subtile fluid, which he called æther: the cistern barometer is then described; after which are detailed the various contrivances for enlarging the scale of the variations of the barometer;—first in order is the barometer of Descartes; then the double barometer of Huygens, the advantages and disadvantages of which are pointed out; next, the more accurate double barometer, and the wheel barometer of Dr Hook; the inclined barometer, ascribed to Sir Samuel Moreland; the square barometer of Cassini and Bernoulli; the conical barometer of Amontons; the sectoral barometer proposed by Magellan; the adaptation of the differential scale for measuring minute divisions, first proposed by Vernier, early in the seventeenth century, but long afterwards strangely neglected;—the article next proceeds to mention the circumstances which influence the variations of the barometer, viz. the effect of moisture within the barometric tube,—the effect of the width of the tube—the uniform convexity of the surface of pure mercury in properly constructed barometers,—the quantity of depression in different tubes, the application of a leather bag to the syphon barometer,—the effect of heat on the barometer, which leads to an account of the successive improvements of the thermometer; marine barometers are next described, the most approved kind of which, manufactured by Mr Cary of London, is illustrated by a figure, in a well executed plate—the difficulty of explaining the variations of the barometer are adverted to, and some hints are thrown out relative to these causes. On the whole, we think this a very able article, though, perhaps, a little too discursive.

As a sequel to the article, we have, from the same pen, a paper on. The decisive experiment by which Pascal ascertained that the pressure of the atmosphere diminished according to its elevation, naturally suggested to him the possibility of measuring by the barometer the relative heights of distant places on the surface of the globe. The first attempts, however, were rude, as they proceeded on the inaccurate supposition that the lower mass of air is a fluid of uniform density. We regret that our limits prevent us from accompanying Mr Leslie in tracing the successive steps by which the instruments and the rules employed in barometrical measurement have attained their present state of perfection. One interesting discovery, however, lately made by this mode of distant levelling, we must, in justice to our readers, mention. Two Prussian travellers, Engalhorde and Parrot, who proceeded, on the 13th July 1814, from the mouth of the Kuban, on the Black Sea, to the mouth of the Terek, on the Caspian, ascertained, by a series of fifty-one accurate observations, that the Caspian is 334 English feet below the level of the ocean; and that, at the distance of 189 miles from the Caspian, the country is depressed to the level of the ocean—thus leaving an immense basin, from which the waters are supposed to have retired by a subterraneous percolation.

In the article, the medical and physical effects of the various kinds of baths, in various circumstances, as determined by the observations of Wright, Currie, Seguin, Parr, Haygarth, Fourcroy, Marcard, and other able physicians, are minutely and accurately detailed.

The article we opened with peculiar interest; and though we are very far from agreeing to the theory proposed, and the reasoning by which that theory is supported, we are ready to do full homage to the abilities displayed in the discussion. We cannot say, however, that we greatly admire the style in which the article is composed. It is distinguished, indeed, by great vigour of conception, and by a command of language almost peculiar to its celebrated author; but the vehemence of its tone, and the dogmatical confidence of its assertions, remind us VOL. I.