that all the produce of the colonies is fent. It is in London that most of the owners of this produce refide. It is in London that the profit arising from it is fpent. The reft of the nation is but very indirectly concerned in it. But London is the finest port in England. It is here that ships are built, and manufactures are carried on. London furnishes feamen for navigation, and hands for commerce. It stands in a temperate, fruitful, and central country. Every thing has a free paffage in and out of it. It may be truly faid to be the heart of the body politic from its local fituation. It is not of an enormous fize, though, like all other capitals, it is rather too large; it is not a head of clay, that wants to domineer over a coloffus of gold. That city is not filled with proud and idle men, who only incumber and opprefs a laborious people. It is the refort of all the merchants; the feat of the national affembly. There the king's palace is neither vaft nor empty. He reigns in it by his enlivening prefence. There the fenate dictates the laws, agreeable to the fenfe of the people it reprefents. It neither fears the eye of the monarch, nor the frowns of the miniftry. London has not arrived to its prefent greatnefs by the influence of government, which ftrains and over-rules all natural caufes; but by the ordinary impulfe of men and things, and by a kind of attraction of commerce. It is the fea, it is England, it is the whole world,, that makes London rich and populous. NATURAL NATURAL HISTORY. An Account of fome curious Articles in the Abbé Rozier's Fifth Volume of Obfervations fur la Phyfique, &c. or, Obfervations in Natural Philofophy, Natural Hif tory, and the Arts, published in Paris, relating to various Experiments lately made in France, to afcertain the Truth of Sir Ifaac Newton's Dorine, concerning the Difference in the Gravitation of Bodies towards the Earth, at different Distances both above and below her Surface. ARTICLE the FIRST. The Judgment of certain impartial Traction, or rather that par- ticular branch of it that relates to tate towards the centre of the earth, in an inverfe ratio of the fquare of the distance. In confequence of this law, it is evident, that the weight of bodies ought to diminish in proportion as they recede from the earth's furface. Father Bertier, however, and feveral other philofophers, affirm, that this propofition is contradicted by the experiments lately made by them. The trials on which they ground their affertion, are of a fimilar - nature to fome that were made in this country, in the last century, by certain members of the Royal Society; who very judiciously inferred from them, that this mode of trial was not adequate to the folution of the queftion. In relating the most effential particulars of one of the experiments made by thefe new Anti-Newtonians, we fhall convey to our philofophical readers fome idea of the manner in which they have, in general, been executed. A ftrong and accurate balance, which would fupport a weight of 3000 pounds, and which would turn on the addition of a fingle ounce weight in either of the bafons, was fixed within the fteeple of a church, at the height of 170 feet from the pavement. The balance was fo conftructed, that af ter loading each bafon, above,"` F with ARTICLE the SECOND. A Memoir, indicating the different Caufes which may accidentally change the apparent Effects of the Gravity of Bodies, placed at unequal Heights: read before the Academy of Dijon. with a weight of 1120 pounds, fo doctrine of attraction, principally as to make a perfect equilibrium; collected from the following ar the weight on one fide could be ticle. lowered, and placed in a fecond bafon, attached to the fame fide by means of a rope, fo as nearly to reach the pavement of the church. In fome of the experiments, ftrong iron wire was em- . ployed instead of the rope. When this weight, which had, above, been in equilibrio with that in the oppofite bafon, had been thus brought 170 feet nearer the furface of the earth; the equilibrium, we are told, was deftroyed, and, inftead of preponderating, in confequence of its fituation, it rofe; fo that it was neceffary to add to the weight in this lower fcale. We obferve, however, that one ounce and fix drachms were found fufficient to restore the equilibrium; and that the balance might be made to incline either to the one fide or the other, on the addition of another ounce to either of the bafons. The reader is not to confider this particular experiment as one of the most favourable to the caufe of the Anti-attractionaires. We relate it chiefly to thew the grounds on which they found their objections to the Newtonian fyftem of, attraction, and the method by which they endeavour to fupport them; obferving only, that in the many other experiments of the fame kind, related in this and other numbers of M. Rozier's work, the refults have been, at different times, more or less favourable to their hypothefis. We fhall next attend to the experiments and reafonings of the oppofite party, who fupport the 4 THE balance that was used in the experiments related in this Memoir, would carry 250 pounds in each bafon; and was fo fenfible, that when it was loaded with this weight, it would turn on the addition of half a drachm. The experiments were made in the tower of a church, at the height of 120 feet. They were conducted nearly in the fame manner as the preceding, and with à fcrupulous attention to every circumftance that might influence the refults. Barometers and thermometers, in particular, were placed both above and below. In the first experiment, the balance, containing on each fide 200 pounds, including the weight of a long rope in one of the bafons, being in perfect equilibrium; this laft-mentioned bafon was let down 120 feet below its former ftation, fufpended by the rope above mentioned. At firft, the equilibrium was fomewhat difturbed by the ofcillations of this lower bafon; fo that it was found neceffary to add two drachms to the upper weight, to render the balance even. This motion, however, at length, ceafing, it was found requifite to take out this fmall additional weight; and then the fuperior and inferior weights weights were obferved to equiponderate, in the fame manner as when they had both been fufpended at the fuperior ftation. As the denfity of the air is greater near the furface of the earth than at different heights above it, the author of this Memoir calculates, from data furnished by other experiments here mentioned, the quantity of the effect which this difference muft produce in the apparent gravity of the upper and lower weights; which were each of cast iron, and equal to two-fifths of a cubic foot. From his calculations it appears, that, in confequence of the difference between the denfity, or weight, of two-fifths of a cubic foot of air at the earth's furface, difplaced by the lower weight, and that of an equal bulk of the fame fluid difplaced by the upper weights, the lower weight ought to weigh 52 grains and three-fifths less than the upper. On the other hand, he calculates the increase of gravity which, according to the Newtonian fyftem, the lower weight ought to have acquired, in confequence of its greater proximity to the furface. Eftimating the femidiameter of the earth to be 3,268,965 toifes, he obferves, that the force with which the lower weights were attracted, is to that which acted on the upper ones, placed 20 toifes higher, and confequently diftant 3,268,985 toifes from the earth's centre, as the fquare of the last number is to that of the firft; and finds that, on this account, the lower weights ought to have acquired an increafe of gravity equal only to 22 grains. As the lower weights therefore ought to have loft 52 grains and three-fifths, in confequence of the density of the air; and, on the contrary, to have acquired 224 grains, in confequence of attraction"; there remains only a difference of 30 grains and one tenth, which is too inconfiderable a quantity to be rendered fenfible in a balance loaded with 500 weight. In the fecond experiment the refults were fimilar, as likewife in a third, in which iron wire was fubftituted for the rope. In a fourth, on ufing a counterpoife, confifting of dry wooden billets, instead of the metal weights, and which were first perfectly poifed above; the billets evidently loft weight, on being let down to within a fmall diftance from the pavement; fo that it was found neceffary to take away feven drachms from the upper bafon to reftore the equili brium. This experiment is prefented as offering an equivocal proof of the influence of the fuperior density of the air, at the lower ftation, in diminishing the relative gravity of bodies weighed in it. In fact, it appears from calculation, that the voluminous wooden counterpoife above mentioned ought to have loft nearly this quantity of its weight, in confequence of the fuperior denfity of the medium in which it was fufpended, independent of any other caufe, THESE experiments, which likewife relate to the preceding queftion, were made in a different order. The fcales were fixed on the furface of the earth, and after procuring an exact equilibrium between the oppofite weights in that' fituation, thofe contained in one of the basons were let down to the depths of 114 and 190 yards, into a coal mine. Sometimes the undermoft weight preponderated, but more frequently the fuperior. The quantity, however, in either cafe, was fo fmall, that the author very properly concludes, from the refults both of his own and the many other experiments that have lately been made on the fubject, that they are infufficient to determine the queftion. In this opinion we readily concur with him; nor fhould we have taken fo much notice of the fubject, were not the question itself of great importance, and had it not likewife been so very extenfively and warmly litigated, of late, among our neighbours on the continent. The experiments which have been produced in fupport of the theory of gravitation have indeed the merit of evincing the feebleness of this late attack upon it; but nothing further is or can be determined from them: nor does the Newtonian fyftem ftand in need of fuch feeble fupports. Non tali auxilio, nec defenforibus iftis, &c. [Monthly Review.] Subftance of two curious Articles in the Second Part of the Sixty-fifth Volume of the Philofophical Tranfacticas, being that for the Year 1775; viz. the Forty-eighth, being A Propofal for measuring the Attraction of fome Hills in this Kingdom by aftronomical Obfervations; by the Rev. Nevil Makelyne, D. D. F. R. S. and Aftronomer Royal; and the Fortyninth, being An Account of Obfervations made in Scotland on the Mountain of Schehallien (at his Majefy's Expence), for finding its Attraction; by the fame Gentleman. HESE two articles contain ΤΗ the hiftory of a late impor tant philofophical expedition, very properly undertaken and executed under the aufpices of the Royal Society; with the intention of afcertaining, by decifive experiments, the truth of the great law of univerfal gravitation :- -the bafis of that noble fyftem which the world owes to the genius and fagacity of Newton. According to the Newtonian theory, an attractive power is not only exerted between thofe large maffes of matter which conftitute the fun and planets; but likewife between all comparatively fmaller bodies, and even between the fmallest particles of which they are compofed. Agreeably to this hypothefis, a heavy body, which ought to gravitate or tend toward the centre of the earth, in a direction perpendicular to its furface, fuppofing the faid furface to be perfectly even and fpherical, ought likewife, though in a lefs degree, to be attracted and tend towards a mountain placed on the earth's furface: fo that a plumbline, for inftance, of a quadrant, hanging in the neighbourhood of fuch |