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Show GR GR Bodies comparatively light, are not really fo, fince it has been found by Experiment iz vacuo, that they defcend asfaft as other Bodies 297 POY wi & 2 OUP Parts ; for by the adding or taking away any Part of the Matter of «a Body, its Gravity is increafed or diminifhed in Proportion to the Quantity offuch Particles to the en:ire Mafs. To this Property of Gravity, perhaps, is owing the alternate Motion of the Sapi getables, which may be accounted forff the Alternacies of the Day and Night, Warm and Cold; Moift and Dry ; for it 1s very probable that the Sap in Plants dovs in fomé meafure recede from the Topsof their Branches, 3dly, The Force of Gravityis nearly equal in all Places equidiftant from the Center of as the Sun leaves them; becaufe its raretying the Earth: But indeed all Places of the Sur- Power then ceafing, the greatly rarefied Sap, face of the Earth are not at equal Diftance from the Center, becaufe the Equatorial Parts thing higherthan the Polar Parts. 4thly, Gravity affects all Bodies equally, Pays fev aor) 2 7? pybredy 2 fs without regardeither to their Bulk, Figureor Matter; fo that abftracting fromthe Refiftance of the Medium, the moft compaé andloofe, the greateft and fmalleft Bodies would defcend qual Spaces in equal Times, as appears from Quicknefs of the Defcent ofvery light in an exhaufted Receiver. Whence we may obferve a very great Difference between Gravity and Magnetifn , Gra- vity affecting all Bodies alike, and Magnetifin affecting only Iron, and that towards its Poles, and Air mix’d with it, will condenfe and take up lefs Room than they did, and the Dew and Rain will. then be ftrongly imbibed by the Leaves, which mixing with the included Sap, will render it too heavy to be fuftain’d by the Preffure of the Air upon the Surface of the Plant, or by any conftriéting Quality of the containing Veffels, fo that it recedes downwards until it meets with an equal Refiftance, whereby it is fufpended until the Return of Warmth, which rarefies the Sap, and renders it fpecifically lighter than before, and fo mounts again to the Extremity of the Branches; and part of it, by being rendet’d extremely light, paffes off thro’ the Pores of the Plant; and is evaporated, And hence we mayalfo conclude, that there is no pofitive Levity; for that thofe Things whieh do feem to be light, are only fo comparatively ; and whereas feveral Things fwim and rife in Fluids, the Caufe is only becaufe they are not fo heavy as thofe . luids, Bulk for Bulk. There is no Reafon that Cork fhould be faid to be light, becaufe it foats upon Water, more than Iron, by reafon that will float on Mercury. ly, This Power increafes in de {cending DOdI towards the Center of the Earth, in Proportion to the Squares of the Diftances romreciprocally ; and alfo decreafes in in the fame Proportion, fo as at Diftance, to have but a quarter of wy YY . yy ye Pa. UY, . yy, ry pu noady ayy ‘: ¢ ¢ [ yp Yet?) 1) ; » fr ye 22h) PUD pry 2 f§ ? poppu natty fs “Y do in Air. The Properties of Gravity are as follow ; ift, That all Bodies do defcend towards a Point, which is either the Center of Magnitude of the Earth and Sea, about -which the Sea forms itfelf into a {pherical Surface, or is very near it. adly, This Point or Center is fixed within the Earth. Hence alfo, the attraétive Force of entire Bodies, confifts of the attraétive Force of the rs very agreeable to Reafon, beitating or attracting Power muft y be excited more feebly in a greater and more vigoroufly in a {inall Sphere, as it is expandedorcontra¢ted. o that the Surfaces of Spheres being to one her as the Squares of the Radii, the Power of them at feveral Diftances will be reciproally as the Squares of thofe Diftances, and n the whole of its A@ion upon each {phe- ce, whether it be great or {mall, will ys equal. 6thly, As all Bodies gravitate towards the I s the Earth equally gravitate tos, i. é. the Aétion of Gre on each Side, and equal. fo the attractive Powers of Bodies, nces from the Center, are as the f Matter in the Bodies GREEN-HOUSE or Confervatory. As of late Years there have been great Quantities of curious Exotick Plants introduc’d into the Engli/h Gardens, fo the Number of: Green-houfes or Conjervatories has increafed, and not only a greater Skill in the Management and Ordering of thefe Plants, has increafed therewith ; but alfoa greater Knowledge of the Struéture and Contrivance ofthefe Places, fo as to render them both Ufetul and Ornamental, hath been acquired: Arid fince there are many Particulars to be obferv’d in the Conftruction of thefe Houfes, whereby they will be greatly improv’d, fo I thought it neceffary, not only to give the beft In{tructions for this I was capable of ; but alfo to give a Defign of one in the Manner I would chufe to erect it, upon the annex’d Copper Plate. Asto the Lengthof thefe Houfés, that muft be proportion’d to the Number ofPlants they are to contain, or the Fancy of the Owner; but their Depth fhould never be greater than fixteen or eighteen Feet in the Clear; and the Length of the Windows fhould be at leaft equal to the Depth of the Houfe, and if they are fomewhat longer, it will be ftill the better : Thefe Windows fhould be carried up quite to the Ceiling, that there may be no Roomfor dead Air in the upper Part of the Houfe ; and they fhould come down within about ten Inches or a.Foot of the Floor ; their Breadth fhouldbe proportion’d to the Length of the Houfe; which in a fmall Green-hou/e, may be four Feet broads but in a large one, they fhould be fix Feet: The Piers between Ccce thefe |