ject of confideration, in these matters, is the comparative ftate of a refidency at any particular period, with what may be justly confidered as its medium ftate. There muft exist a determinate proportion, between any number of bearing vines, and fuch a number of young as are neceffary to replace them when they go off and keep up a regular fucceffion. This will depend in general upon the length of time before they reach a bearing ftate, and during which they afterwards continue in it. If this certain proportion happens at any time to be disturbed, the produce must become irregular. Thus, if at any period, the number of bearing vines hall be found to exceed their juft proportion to the total number, the produce, at fuch period, is to be confidered as above the mean, and a fubfequent decreafe may be with certainty predicted, and vice versâ. If then this proportion can be known, and the ftate of population in a refidency afcertained, it becomes eafy to determine the true medium number of bearing vines in that refiden cy. "There are, agreeably to the form of the furvey book, eleven stages or claffes of vines, each advanced one year. Of thefe claffes, fix are bearing, and five young. If there fore the gardens were not liable to accidents, but paffed on from column to column undiminified, the true proportion of the bearing vines to the young, would be as fix to five, or to the total, as fix to eleven. But the various contingencies above hinted at, must tend to reduce this proportion; while on the other hand, if any of the gardens fhould continue longer than is neceffary to pafs through all the ftages on the furvey-book, or should remain more than one year in a prime ftate, thefe circumstances would tend to increase the proportion. What then is the true medium proportion, can only be determined from experience, and by comparing the ftate of a refidency at various fucceffive periods. In order to afcertain this point, a very ingenious gentleman, and able fervant of the Eaft India company; to whom I am indebted for the most part of what I have laid before the reader on this fubject; drew out, in the year 1777, a general comparative view of Manna refidency, from the furveys of twelve years, annexing the produce of each year. From the statement it appeared, that the proportion of the bearing vines to the whole number, in that district, was no more than 5,1 to 11, inftead of 6 to 11, which would be the proportion if not reduced by accidents: and farther, that when the whole produce of the twelve years was diffufed over the whole number of bearing vines during that period, the produce of one thou fand vines came out to be four hundred and fifty-three pounds, which must therefore be eftimated as the medium produce of that refidency. The fame principle of calculation being applied to the other refidencies, it appeared, that the mean annual produce of one thoufand vines, in all the various stages of bearing, taken collectively throughout the country, deduced from the experi ence of twelve years, was four hun dred and four pounds. It likewise became evident from the statements drawn out by that gentleman, that the medium annual produce of the company's fettlements on the weft coaft of Sumatra, ought to be eftimated at twelve hundred tons, of fixteen hundred weight; which is corroborated by an average of the actual receipts for any confiderable number of years." ACCOUNT ACCOUNT of Monf. De St. FOND's DESCRIPTION of EXPERIMENTS made by the AEROSTATIC MACHINE. [From the Appendix to the fixty-ninth Volume of the MONTHLY REVIEW.] "WE avail ourselves of the op. common fized bladders. portunity of this recent publication, to lay before our readers a brief historical account of the very interesting difcovery which has of late attracted the notice of the whole philofophical world; and which our fanguine neighbours did not feruple, at the very firft, to dig nify with the name of Aerial Navigation. "Although the author of this book be known to have warmly ef poufed the party of Montgolfier, in oppofition to that of Charles (for there are parties even concerning balloons), yet his reputation, as a man of learning and veracity, is fufficiently established, and the facts he here alleges are in general, as we have had opportunities to afcertain by collateral evidence, ftated with fufficient accuracy to justify us in taking him for our guide in this narrative. "The preface contains a fhort furvey of what projects have formerly been fuggefted for the purpofe of floating heavy bodies in the atmosphere; the principal of which are thofe of Lana, a Jefuit of Bref cia, and of Galien, a Dominican of Avignon, both which however were, upon well-established principles, found by theory to be impoffible in the execution. Due honour is paid to Mr. Cavallo of London, who, in 1782, feemingly with a view to this difcovery, tried to fill bags of paper and bladders with inflammable air; but failed in his attempts, by the unexpected permeability of paper to inflammable air, and the too great proportional weight of the Had he then thought of employing gummed filk, or gold beater's kin, he probably would have plucked the very laurels that now adorn the brows of Montgolfier and Charles. " I. The honour of the difcovery is certainly due to the brothers Stephen and Jofeph Montgolfier, proprietors of a confiderable paper manufacture at Annonay, a town in the Vivarais, about thirty-fix miles fouth of Lyons and their invention is the more to be admired, as it is not the effect of the late difcovery of a permanent elastic fluid, lighter than the common air, but of properties of matter long known, and in the hands of the many acute philofophers of this and of the laft century. They conceived that the effect they looked for might be ob tained by confining vapours lighter than the common air, in an inverted bag, or covering, fufficiently compact to prevent their evapora tion, and fo light, that when inflated, its own weight, added to that of the inclofed vapour, might fall fomewhat fhort of the air which its bulk difplaces. "On thefe principles, they prepared matters for an experiment. They formed a bag, or balloon, of linen cloth, lined with paper, nearly fpherical, and meafaring about 35 feet in diameter; its folid contents were about 22,000 cubic feet, a space nearly equal to that occupied by 1,980lb of common air, of a mean temperature, on the level of the fea.-The vapour, which, by conjecture, was about half as light as common air, weighed 990lb. The The balloon, together with a wooden frame fufpended to the bottom, which was to ferve as ballaft, weigh ed 490lb. whence it appears that the whole must have been about 500lb. lighter than an equal bulk of common air. This difference of fpecific gravity, by which thefe bodies are made to rife, we fhall henceforth, without warranting the propriety of the expreffion, call their power of afcenfion. "The 5th of June 1783, was fixed on for the difplay of this fingular experiment. The ftates of Vivarais, who were then affembled at Annonay, were invited to the exexhibition-The flaccid bag was fufpended on a pole 35 feet high; itraw and chopped wool were burnt under the opening at the bottom; the vapour, or rather fmoke, foon inflated the bag, fo as to diftend it in all its parts; and, on a fudden, this immenfe mafs afcended in the air with fuch a velocity, that in lefs than ten micutes it appeared to be About 1000 toifes above the heads of the fpectators. A breeze carried it about 120 toifes from the fpot whence it departed; and then the vapour, either efcaping through fome loop holes that had been accidentally left in the conftruction, or being condenfed by the coldness of the circumambient air, the globe defcending gradually on a vineyard, with fo little preflure, that none of the ftakes were broken, and fcarce any of the branches of the vines bent. "II. The rumour of this fuceefsful experiment foon reached the metropolis, and roufed the emulation of the Parifian philofophers. Without waiting for particular instructions from the inventors, they concluded on a method of their own; and refolved, instead of vapour to ufe inflammable air; the fpecific weight of which, when pure, they knew to be to that of common air nearly as one to ten. : "The process of producing this air being very expenfive, the author of the book now before us, fet on foot a fubfcription; and having foon raised a fufficient fum, M. Charles, profeffor of experimental philofophy, and M. Robert, a mathematical inftrument-maker, were fet to work and they conftructed a globe of luteftring (taffetas), glazed over with elaftic gum diffolved in fome kind of fpirit or effential oil. After many difficulties and disap pointments, which will ever attend firft effays, they fucceeded, in two days, to fill this globe with inflam mable air, produced from 1000lb. of iron-filings and 4981b. of vitriolic acid, diluted in four times its quantity of water. This globe mea. fured 12 feet 2 inches in diameter, its folid contents were 943 feet 6 lines cubic, and its power of afcen fion was found equal to 35lb. "The 27th of August 1783, having been fixed on for the exhi bition of this experiment, the bal loon was conveyed, in the preceding night, floating in the air, from a court near the Place des Victoires, where it had been constructed, to the Champ de Mars. Our author indulges his lively imagination in a lofty defcription of this nocturnal proceffion, which, he fays, moved along in the dead of night, at tended by a party of guards, with lighted torches, and feemed fo aw. ful, that the hackney-coachmen who happened to be in its way, def cended from their feats, and devout. ly proftrated themfelves before the fupernatural being that advanced in fuch folemn state. "The concourfe of people, on foot and in carriages, was fo im menfe in the Champ de Mars, that a large a large body of troops were drawn out to prevent disturbances. At five o'clock in the afternoon, a fignal having been given by the firing of a mortar, the cords that confined the globe were cut, and it rofe, in less than two minutes, to a height of near 500 toifes.-It there entered a cloud, but foon appeared again, afcending to a much greater height: and at laft it was loft among other clouds. "Our author juftly cenfures the conduct of this experiment; obferving, that too much inflammable air, and that even fome common air had been introduced into the globe, which being clofed on all fides, left no room for the expanfion of this elaftic fluid when it thould arrive to a more rarefied medium. We find, in fact, that it must have burft in confequence of this expantion; fince, after having floated about three quarters of an hour, it fell in a field near Goneffe, a village about five leagues (15 miles) N. N. W. of the Champ de Mars. It must be allowed, that the mere evaporation of the air could not well have been the caufe of its defcending fo foon. Many periodical papers have already entertained the public with ludicrous accounts of the aftonifhment of the peafants who found it, and of the rough treatment it received at their hands. "III. It may eafily be imagined, that thefe brilliant fucceffes animated the zeal of all the curious in the metropolis; and that many effays were made to repeat the fame experiments upon a fmaller fcale. Our author, accordingly, in a third chapter, mentions a number of thefe fecondary attempts; upon which we fhall dwell no longer, than only to obferve, that they fucceeded with globes made of gold-beaters skin, and only 12 inches in diameter, which being thought the leaft that could be made to afcend, confidering that the proportionate weight of the materials increases as the bulk is diminifhed, were called minimums. "IV. M. Montgolfier, junior, having arrived at Paris, a few days before the experiment at the Champ de Mars, was defired by the Royal Academy of Sciences to repeat the experiment of Annonay. He accordingly constructed, in a garden, in the Fauxbourgh St. Germain, a balloon of an elliptical form, 70 feet high, and 40 feet in diameter. It was lined, both infide and outfide, with paper. its power of afcention was found, upon calculation, to be about 1250lb. It was filled in ten minutes by the burning of 50lb. of straw and 10lb. of chopped wool. It was loaded with a weight of 500lb. and afcended, faftened to ropes, on the 12th of September, in the prefence of the deputies of the Royal Academy.But it proving a very rainy day, the whole apparatus was fo effentially damaged, that it was not thought proper to fet it loofe. V. We come now to the expe. riment made on the 10th of September, in the prefence of the king and queen, the court, and all the Parifians who could procure a conveyance to Versailles. This balloon was 57 feet high and 41 in diameter. Its power of afcenfion, allowing for a wicker cage, containing a fheep, a cock, and a duck, which was fufpended to it, was equal to 696lb. As only four days had been allowed for the making this machine, it could not, therefore, be lined with paper. M. M. had predicted, that it would remain in the air about 20 minutes; and, with a moderate wind might float to a distance of about 1000 toifes. But, befide fome impaction in the 5 construction, conftruction, owing to the great hurry in which it had been made, a fudden gust of wind, whilst it was inflating, made two rents feven fect long near the top, which could not but in fome meafure prevent the promifed effect. It fwelled however in 11 minutes fufficiently to raise it about 240 toifes; it floated to the diftance of nearly 1,700 toifes, and, after having been in the air about eight minutes, it fubfided gradually in the wood of Vaucreffon.-The animals in the cage were lately landed. The fheep was found feeding; the cock had received fome hurt on one of his wings, probably from a kick of the fheep: the duck was perfectly well. "VI. M. Montgolfier, determined now to repeat the experiment under more favourable circumftances, and more at his leifure. He therefore made a new balloon, in a garden, in the Fauxbourgh St. Antoine, which meafured 70 feet in height, and 46 feet in diameter. A gallery of wicker was contrived round the aperture at the bottom; under which an iron grate or brazier was fufpended, and port holes opened on the infide of the gallery, towards the aperture, through which any perfon cui robur et as triplex circa pectus fuerit, who might venture to afcend, might feed the fire on the grate, and thus keep up the vapour, fmoke, or as rather we apprehend, the dilatation of the air, in this vaft cavity. "On the 15th of October, M. Pilatre de Rozier, no doubt the most intrepid philofopher of the age, placed himself in the gallery, afcended about eighty feet from the ground, and there kept the balloon afloat for fome time, by repeatedly throwing ftraw and wool upon the fire. In this experiment it was found, that the defcent of a globe (provided no extraordinary accident happened to it) must neceffarily be gradual; and that it will always light foftly upon the ground, fince, in fact, in every part of its defcent, it enters a denter medium; whence its velocity in falling will rather be retarded than accelerated. On the 19th of October, M. P. de R. afcended a fecond time, about 250 feet. After continuing ftationary a bout eight minutes, a gust of wind carried the balloon among fome trees, where it entangled itself so as to endanger its being torn to pieces. But on M. R. throwing fome fresh ftraw upon the fire, it immediately reafcended, amid the loud acclamations of a vast multitude of people, who little expected to fee fo fudden a recovery. The balloon was then hauled down, and M. Giron de Villette placed himself in the gallery oppofite to M. R. They were once more let up; and for fome time hovered over Paris, in the fight of all its inhabitants, at the height of 324 feet. "VII. Matters feemed now ripe for a free aerial navagation. A fmoke balloon, very fimilar to the one laft defcribed, was prepared to go off at La Muette, a royal palace in the Bois de Boulogne, where, we are infromed, the king's children, now ufually refide. All things being ready, on the 21ft of November, M. Pilatre de Rozier took his poft in the gallery; and the marquis D'Arlandes, a major of infantry, placed himfelf on the oppofite fide of this gallery, as a counterpoife to preferve the equilibrium of the machine. After repairing fome damage done to the balloon in a first effay, it was, at 54 minutes after one, abfolutely abandoned to the element; and it ascended with great rapidity. "When these bold adventurers were |