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Upon the whole we may observe, that of the 6 lbs. of aliment taken in a day, there appears to be nearly 1 lb. of carbon and azote together; the remaining 5 lbs. are chiefly water, which seems necessary as a vehicle to introduce the other two elements into the circulation, and also to supply the lungs and other membranes with moisture. Very nearly the whole quantity of food enters into the circulation; for the fæces constitute only oneeighteenth part, and of these a part, bile, must have been secreted; one great portion is thrown off by means of the kidneys, namely about half of the whole weight taken, but probably more or less according to climate and season, &c.; another great portion is thrown off by means of insensible perspiration, this last may be subdivided into two portions, one of which goes off by the skin, amounting to one-sixth part, and the other five-sixths are discharged from the lungs in carbonic acid, and in water or aqueous vapour.

Such are the deductions I have drawn from my early experiments, and from the light which modern chemistry has diffused over the animal and vegetable products. This branch of science belongs more peculiarly to the physician. What the profession may have done in it of late years, I am not aware, my studies not having been in that line. But it must be allowed to be a subject worthy the attention of professional characters, and not uninteresting as a branch of physics.-Memoirs of the Manchester Philosophical Society, Second Series, vol. v.

Barometric Measurement of the Height of Cheviot. By Lieutenant-Gen. Sir THOMAS MAKDOUGALL BRISBANE, K. C. B., President of the Royal Society of Edinburgh, LL.D. &c., and Mr WILLIAM GALBRAITH, Oxon., A. M.

FROM

ROM repeated measurements of altitudes by the barometer, carefully performed, various important consequences may be deduced relative to the expansion of air, affected with temperature and different degrees of moisture. By the same means the decrements of heat, in proportion to the height, of which the law is not yet probably so well determined as might be desirable, will also be determined. With these views, it was agreed by the observers just named, to make a series of observations at

Holy Island, where Sir T. M. Brisbane was residing, and where he had a good set of instruments for the purpose; while Mr Galbraith, with another set of similar instruments, should make a corresponding series on the top of Cheviot, at times previously agreed upon.

On the 14th of September 1832, two corresponding series were made, under rather favourable circumstances, between the hours of 11 and 12 noon, of which the following are the means, indicated by general symbols.

At Holy Island, 59 feet above the mean level of the sea,

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on the top of Cheviot, near the eastern extremity, and a few feet under the mark lately erected by Sir T. M. Brisbane, in the place of that formerly occupied by the theodolite, used in the trigonometrical survey *,

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In like manner, a series was taken in Mr Adie's shop, 58. Prince's Street, Edinburgh, at 207 feet above the mean level of the sea at Leith, by Mr R. Adie, to see what influence horizontal distance might have on the results, where

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In which B denotes the height of the mercury in the barometer at the lower station, the temperature of the mercury in the barometer by the attached thermometer, t that of the air by the detached thermometer, while b, ', and ť, mean the same at the higher stations, though, for the purpose of avoiding all uncertainty of the real temperature of the mercury in the barometer tube and cistern, it has been thought desirable, in these observations, to allow both thermometers to come to the same temperature, by exposing the instruments to the free action of the atmosphere for an hour before recording the observations from which the deductions are made, since it appears doubtful that

It is much to be regretted that substantial permanent marks, which might have been prepared at a trifling additional expense, are not universally left by the Ordnance surveyors at all their stations; such as a roughly dressed block of stone, with the King's mark, the arrow, upon it, and a cross to point out the exact centre of the theodolite, as it is probable that, in the course of a very few years, they will be generally irrecoverably lost.

the attached thermometer shews it in every case, however unequally the instruments may be affected by heat from the observer's body, or other causes.

As barometers, however well made, even by the same artist, show small differences from one another, depending upon slight variations in the specific gravity of the mercury, its different degrees of purity, and the perfection of the construction, it was considered indispensable to institute a rigorous comparison, to determine the differences, which have been denominated Index Errors. If, therefore, Sir T. M. Brisbane's barometer be called A, Mr Galbraith's B, Mr Adie's C, then A being taken as a standard, the index errors will be

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that is, if the three barometers were all standing together on the same level, and having the same temperature, it would require 0.093 inch to be added to the height read from Mr Galbraith's barometer B, to render it the same as Sir Thomas Brisbane's, and it would require 0.108 inch to be added to Mr Adie's, C, to make it of the same height as Sir T. M. Brisbane's. These numbers were obtained by comparing Mr Galbraith's barometer, first with Sir T. M. Brisbane's at Holy Island, and afterwards at Edinburgh with Mr Adie's. tions being applied,

Sir Thomas Brisbane's will shew

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B

=

Whence, these correc

29.849, 7= 57.0, t = 57.0.

Mr Galbraith's, corrected, will give

b 26.993

Index error + 0.043

Corrected b= 27.086, 7′ = 44.5, ť′ – 44.5.

Mr Adie's, corrected, will give

=

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With these, then, the final results are determined by the formula investigated in this Journal for October 1831,

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which exceeds the other by 11 feet, a quantity not very great, considering the distance, and the weather not in the most favourable state. It shows, however, that even at considerable distances, such as 50 or 60 miles, in this case, as well as in our measurement of the height of Benlomond in 1828, that considerable accuracy in the results may be expected, when the observations are carefully made with good instruments.

The important consideration of the decrement of heat, according to the distance from the earth's surface, may now be considered. From various measurements of heights by Messrs Galbraith, Adie, Henderson, &c., it will appear, that, near the surface of the earth, in this country; at about latitude 56° N., Fahrenheit's thermometer falls about 1° for 70 yards of ascent, in heights not exceeding 2000 or 3000 feet. Thus, the mea

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It may, therefore, be concluded, that, to depress the thermometer 1°, near the surface of the earth, the ascent of 70 yards, or 210 feet, in round numbers, must, in this climate, be pretty near the truth. It is probable, however, that this does not hold good either towards the equator or poles.

By analyzing the results recorded in Ramond's work on the barometric formula, it will be found that this increases with the height. In heights of 5000 feet, the elevation necessary to depress the thermometer 1°, is about from 230 to 250 feet, obtained by dividing the height by the difference of temperature*. In fact, it may, a priori, be inferred, that at immense distances in absolute space, from any of the celestial and planetary bodies, where no contiguous body exists to influence the thermometer, that it could be moved considerably in any direction, without any change of its indications. From some late investigations relative to astronomical refractions, similar inferences have been made.

It may therefore be concluded, as well from experiment as general reasoning, that the ascent for 1° increases with the height, though the irregularity of this quantity derived from different observations, so liable to be affected with extraneous causes, renders an investigation of the law of increase difficult and somewhat uncertain. From a consideration of various re

* Hence it follows, that at the highest point the depression for 1° must be somewhat more than the mean for the whole, and that near the surface it must be less.

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