damp ftraw, or other materials mixed with brimftone, foot, &c. on fire. Smoke itself is faid to prevent the fly, and, if fo, it will still act more powerfully when mixed with fuch mateterials. It has been obferved in Sweden, that the hops grow naturally among heaps of ftones or fragments of rocks. They therefore advife to cover the ground round their roots with ftones, which will prevent the infects lying their eggs near the roots in the ground, where they lay them to be protected during the winter. The ftones will alfo preferve moisture at the roots during the fummer. A rope cannot be drawn across a plantation of hops, as it can across a field of corn, in cafe of mildew. Here water to wash off the clammy juice that intices and feeds infects feems to be the only remedy. The plantation being well ventilated, may at feaft prevent the frequency of it. The forcing-pump will most effectually wafh off this exudation. Belides infects, there are other animals which are deftructive to corn and grafs. Various animals destroy the roots of grafs to a confiderable distance. Strong lime-water poured on the earth kills them, and foon brings up fine fweet grafs. Moles are of that number. An old writer on agricult advifes to bore a hole in a waln aell, and fill the fame with chaf ofia, and brimstone; fet them on fire in a hole newly dug, fo that the wind may blow the fmoke into it, and other holes being fhut up, and the fmoke will either kill them or drive them away. He alfo advifes to put a live mole in an earthen pot, which fer in the earth to the brim; and the moie, finding he cannot efcape, will ery, which will bring all thofe within hearing to help him our, and fo may be taken. In March, which is the time of their breeding,, numbers of their young-ones may be destroyed by turning up their nefts, which are generally in the largest hills; and the old ones, who will come to look after their young, may be alfo deftroyed. The fmell of a weafel will drive them away. Oil in which lupins have been steepped will kill ants. Brimftone, mixed with rags and the earth of their hills, all fet on fire, will drive them away. It is an obfervation of the Romans, that weevils, and other creatures of that kind, have a great averfion to river crawfish. In France, they throw live lobfters on wheat in granaries when infefted with them; and in a few hours the weevils will come from all parts, difperfing themselves on the walls, and thus are eafily destroyed. It is faid that rue, or the juice of it, in poultry-houfes, will drive away weafels. Where hedges are thin, they may be thickened in the following manner: Gather the feeds of the bramble and white-thorn (being ripe,) mix them with the meal of tares and water till they are of the thickness of honey. This is laid on old ropes or veam, so to remain all the winter. In the Autumn dig trenches a foot and a half deep, where the hedge is to be thickened, or made to remain fo all the winter. At the end of February, lay the rope in the trench, covered with fine mould, watering them, if neceffary; and fo will they in thirty days come up. In Spain, they rub the feeds of the whitemulberry on ropes of bafs, and in the fame manner lay the ropes in trenches, and the young plants fpring up. This practice may be advantageously followed in England now that the railing of filk-worms is generally pursued. Though feemingly foreign to the fubject, I cannot help highly cenfuring the neglect of permitting ivy-vines, which grow on foreft-trees, to remain attached to them. Their roots entering into the bark rob the trees of much of their nourishment; they in a manner ftrangle their fupporters,byimpeding the circulation of their juices, and, in time, deftroy the trees. They fhould be torn up by the roots; for, if any part of them adhere to the tree, they they will spread, as they obtain remained on the furface. In this nourishment by their adhering roots. mould he fet cuttings of the plants he wished to rear, and over them he laid a cover of glafs in a frame, which fitted fo exactly that the water could not exhale. In this fituation, expofed to the warmth of the fun, the cuttings made fresh fhoots; and he obferved, that in proportion as the fhoots rofe upwards, freth roots grew downwards. Having already mentioned Mr Green, I fhall here add another inftance of his ingenuity. As it takes fome time to rear up flowering-fhrubs or plants from the feed, he difcover ed a more expeditious method. For this purpose, he had a box made of fuch a fize as he defired. The joining of the feveral parts were dove tailed into one another, and the joinings were covered with pitch, fo as to become water-tight. He filled the box, perhaps, half full of rich mould, and added water enough to render it fo moift as that the water The cuttings were kept in this ftate till he judged that they had taken fufficient roots to bear being transplanted. And in this manner he was conftantly fupplied with plenty of blowing plants. AGRICOLA Account of the Discovery of a Sixth and Seventh Satellite of the Planet Saturn; with Remarks on the Conftruction of its Ring, its Atmosphere, its Rotation or an Axis, and its spheroidical Figure. By William Herfchel, LL. D. F. R. St. IN Na fhort Poftfcript, added to my laft Paper on Nebula, I announced the discovery of a fixth fatellite of Saturn, and mentioned, that I intended to communicate the particulars of its orbit and fituation to the Members of the Royal Society, at their next meeting. I have now the honour to prefent them, at the fame time, with an account of two fatellites inftead of one; and have called them the fixth and feventh, though their fituation in the Saturnian fyftem intitles them, very probably, to the first and fecond place. This I have done to the end that in future we may not be liable to mistake, in referring to former obfervations or tables, where the five known fatellites have been mamed according to the order. they have hitherto been fuppofed to hold in the range of diftance from the planet. It may appear remarkable, that thefe fatellites fhould have remained fo long unknown to us, when, for a century and an half paft, the planet to which they belong has been the object of almoft every aftronomer's curiofity, on account of the fingular phenomena of its ring. But it will be feen prefently, from the fituation and fize of the fatellites, that we could hardly expect to discover them till a telescope of the dimenfions and aperture of my forty-feet reflector fhould be conftructed; and I need not obferve how much we Members of this Society must feel ourselves obliged to our Royal Patron, for his encouragement of the fciences, when we perceive that the difcovery of thefe fatellites is entirely owing to the liberal fupport whereby our most benevolent King has enabled his humble aftronomer to compleat the arduous undertaking of constructing this inftrument. The planet Saturn is, perhaps, one of the most engaging objects that aftronomy offers to our view. As fuch it drew my attention fo early as the year 1774; when, on the 17th of March, with a 5 feet reflector, I faw its ring reduced to a very minute line. On the 3d of April, in the fame year, I found From the 30th Vol. of the Phil. Tranf. just published, the the planet as it were, ftripped of its noble ornament, and dreffed in the plain implicity of Mars. I pafs over the following year, when with a 7 feet reЯector, I faw the ring gradually open, and exhibit a dark broad line upon it, which I delineated from nature, on the 20th of June 1788, by means of a very good 10 feet reflector. It should be noticed, that the black difk, or belt, upon the ring of Saturn, is not in the middle of its breadth; nor is the ring fubdivided by many fuch lines, as has been reprefented in divers treatises of aftronomy; but that there is one fingle, dark, confiderably broad line, belt, or zone, upon the ring, at least upon the northern plane. The fouthern one, which is lately come to be exposed to the fun, will fhortly be opened fufficiently to enable me to give alfo the fituation of its belts, if it fhould have any. From my obfervations it appears, that the zone on the northern plane of the ring is not, like the belts of Jupiter or thofe of Saturn, fubject to variations of colour and figure; but is moft probably owing to fome permanent conftruction of the surface of the ring itfelf. That, however, for inftance, this black belt cannot be the fhadow of a chain of mountains, may be gathered from its being visible all round the ring; for at the ends of the anfæ there could be no fhades vifible, on account of the direction of the fun's illumination, which would be in the line of the chain; and the faine argument will hold good against fuppofed caverns or concavities. It is moreover pretty evident, that this dak zone is contained between two concentric circles, as all the phenomena answer to the projection of fuch a zone. As to the furmife, which might occur to us, of a divifion of the ring, or rather of two rings, one about the other, with the diftance of an open Space between them, it does not ap pear eligible to venture on fo artificial a construction, by, way of explaining a phenomenon that does not abfolutely demand it. If one ring, of a breadth fo confiderable as that of Saturn, is juftly to be esteemed the most wonderful arch that, by the laws of gravity, can be held together, how improbable muft it appear to fuppofe it fubdivided into narrow flips of rings, which by this feparation will be deprived of a fufficient depth, and thus lofe the only dimenfion which can keep them from falling upon the pla net! It is however true, that as yet we do not know of the rotation of the ring, which may be of fuch a proper velocity as greatly to affift its ftrength; and that, in the fubdivifions, of course the different velocities for each divifion may be equally fuppofed to keep them up. If the fouthern plane fhould prove to be very differently marked, it will at once remove every furmise of fuch a divifion; but if it fhould offer us the fame appearance of a dark zone, in the fame fituation, and of an equal breadth with the one I have obferved on the northern fide, I would ftill remark, that, fince a most effectual way to verify the duplicity of the ring is within our reach, it will be the best way to fufpend our judgment till that can be put to the trial. The method I allude to is an occultation of fome confiderable ftar by Saturn, when, if the ring be divided, it will be feen between the openings, as well as between the ring and Saturn. With regard to the nature of the ring, we may certainly affirm, that it is no lefs folid and fubftantial than the planet itself. The fame reafons which prove to us the folidity of the one will be full as valid when applied to the other. Thus we fee the fhadow of the body of Saturn upon the ring, according to the oppofite fituation of the fun. If we deduce the quantity of matter contained in the body, from the power whereby the fatellites are kept in their orbits, and the time of their revolution, it must be remem bered, bered, that the ring is included in the refult. It is alfo in a very particular manner evident, that the ring exerts a confiderable force upon these revolving bodies, fince we find them ftrongly affected with many irregularities in their motions, which we cannot properly afcribe to any other caufe than the quantity of matter contained in the ring; at leaft we ought to allow it a proper fhare in the effect, as we do not deny but that the confiderable equatorial elevation of Saturn, which I fhall establish hereafter, must also join in it. The light of the ring of Saturn is generally brighter than that of the planet: for inftance, April 19, 1777, I faw the fouthern part of the ring, which paffed before the body, very plainly brighter than the difk of Saturn, on which it was projected; and on the 27th of the fame month, I found, that with a power of 410, my feven-feet reflector had hardly light enough for Saturn, when the ring was notwithstanding fufficiently bright. Again, the 11th of March 1780, I tried the powers of 222, 332, and 449, fucceffively, and found the light of Saturn lefs intense than that of the ring; the colour of the body, with the high powers turning to a kind of yellow, while that of the ring ftill remained white. The fame refult happened on June 25, 1781, with the power 460. I come now to one of the most remarkable properties in the conftruction of the ring, which is its extreme thinnefs. The fituation of Saturn, for fome months paft, has been particularly favourable for an inveftigation of this circumftance; and my eperiments have been fo complete, that there can remain no doubt on this head. When we were nearly in the plane of the ring, I have repeatedly feen the firft, the fecond, and the third fatellites, nay, even the 6th and seventh, pafs before and behind the ring in fuch a manner that they ferved as excel- barely barely visible with my forty-feet reflector, even while the planet was in the meridian; however, we were then a little inclined to the plane of the ring, and the third fatellite, when it came near its conjunction with the first, was fo fituated, that it must have partly covered the firft a few minutes after the time I loft it behind my houfe. In all these obfervations the ring did not in the leaft interfere with my view of the fatellites. October 16. I followed the fixth and seventh fatellites up to the very disk of the planet; and the ring, which was extremely faint, oppofed no manner of obftruction to my feeing them gradually approach the difk, where the feventh vanished at 21 h. 36′ 44′′, and the fixth at 22 h. 36′ 44′′. I might bring many other inftances, if the above were not quite fufficient for the purpofe. There is, however, fome confiderable fufpicion, that, by a refraction through some very rare atmosphere on the two planes of the ring, the fatellites might be lifted up and depreffed, fo as to be come visible on both fides of the ring, even though the ring fhould be equal in thickness to the diameter of the fmalleft fatellite, which may amount to a thousand miles. As for the argument of its incredible thinnefs, which fome aftronomers have brought from the fhort time of its being invifible, when the earth paffes through its plane, we cannot fet much value upon them; for they must have fuppofed the edge of the ring, as they have alfo reprefented it in their figures, to be fquare; but there is the greatest reafon to fuppofe it either fpherical or fpheroidical, in which cafe evidently the ring cannot difappear for any long time. Nay, I may venture to fay, that the ring cannot poffibly difappear on account of its thinnefs; fince, either from the edge or the fides, even if it were fquare on the corners, it must always expofe to our fight fome part which is illuminated by the rays of the fun and that this is plainly the cafe, we may conclude from its being visible in my telescopes during the time when others of lefs light had loft it, and when evidently we were turned towards the unenlightened fide, fo that we must either fee the rounding part of the enlightened edge, or elfe the reflection of the light of Saturn upon the fide of the darkened ring, as we see the reflected light of the earth on the dark part of the new moon. I will, however, not decide which of the two may be the cafe; efpecially as there are other very ftrong reafons to induce us to think, that the edge of the ring is of such a nature as not to reflect much light. I cannot leave this fubject without mentioning both my own former furmifes, and thofe of feveral other aftronomers, of a fuppofed roughness in the furface of the ring, or inequality in the planes and inclinations of its fat fides. They arofe from feeing lumi nous parts on its extent, which were fuppofed to be projecting points, like the moon's mountains; or from feeing one arm brighter or longer than another; or even from feeing one arm when the other was invifible. I was, in the beginning of this feason, inclined to the fame opinion, till one of thefe fuppofed luminous points was kind enough to venture off the edge of the ring, and appeared in the shape of a fatellite. Now, as I had collected every inequality of this fort, it was eafy enough for me afterwards to calculate all fuch furmifes by the known periodical time of the first, second, third, fixth, and feventh fatel lites; and I have always found that fuch appearances were owing to fome of these fatellites which were either before or behind the ring. The 20th of October, for inftance, at 22h. 35′ 46′′, I faw four of Saturn's fatellites all in one row, and at almost an equal diftance from each other, on the following fide; and yet the first fatellite, which was the fartheft of them |