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62.

stable place, and counting ye time it takes to run thrô a certain place as of 3 or 40 feet.  Now supposing ye wind makes 24 feet in one second, as it makes when it is very violant ordinarily however it is much lefs swift than it is in great tempest and Hurricannes it will go as swift as a spout of water wch goeth out of a hole at ye bottom of a reservatory of 12 feet and because ye wind ought to go 24 times as swift as water to produce ye same effect, it shall do no more than water of a like bulk wch goeth but one foot in a second, or a spout wch makes 24, if ye largeness of ye wind is 24 times as great in diameter, or 576 times more in surface.  Now a spout of water of half a foot square coming from a reservatory of 12 feet heigh, may sustain as hath been said above a weight equall to ye weight of a square column of water wch hath for its height 12 feet, and for as much as a semicircle weighs 8 3/4 pounds, if we double that height it shall be 17 1/2 pound for a square column of a foot heigh and of half a foot large, and if it is 11 feet heigh, it shall be 210 pound wch shall be sustained by a spout of half a foot square.  To ye end therefore that ye wind wch goeth as swift may sustain ye same weight of 210 pounds it is necessary that ye sayl it shocs be 24 times as large and as long as 1/2 foot, that is to say it is necessary that it be 12 foot both large and long or 6 foot large and 24 foot heigh, and then ye wind wch shall make 24 foot in a second, will sustain 210 pound placed upon a horizontal rule joyned to ye same axis as ye square sayl of 12 feet, in ye same distance from ye axis, as ye middle of ye length of that sayl wch ought to be in a perpendicular situation, [[strikethrough]] it will support [[/strikethrough]] but if ye wind goeth but 12 feet in a second, it will support but 52 1/2 pounds wch is ye 4th of 210 pounds.

  If we would make experiment in little, it is necessary to make use of ye turnpike of (p 60,_____ and take a sayl of a foot large and heigh, wch having its surface of a foot will support but ye 144th part of 52 1/2 viz 5 1/6 ounces, if that weight is at ye same distance from ye axis as ye middle of that small sayl, but we must choose a wind wch can make 12 foot in a second.

  By this means ye different forces of water and wind by their shoc may be easily calculated.

  To compare a force of ye windmills to that of ye mills of ye river Seine whereof I have spoken, I suppose that each of ye 4 sayls is 30 foot heigh and 6 foot large, these are 180 feet;  if ye wind makes but 12 feet in a second it sustains 5 8/9 of a pound in strikeing a sayl of a foots surface, but if it strikes one of 180 feet in surface it will sustain 66 pounds near:  But there must be taken away 5/8 because of ye triple obliquity is of 30 degrees, there will remain therefore 29 pound and ye four sayls will sustain 100 pound;  but ye distance of ye axis to ye middle of ye sayl is 20 feet, and that of ye middle of shovels to their axis is but 4 feet.  Therefore for that cause ye windmills augment their force 5 fold and if ye toothed wheel of each is of 2 feet diameter, ye force of ye windmill shall be 10 times 100 and that of ye watermills 2 times 466 pounds when ye wind goeth 12 feet in a second, and ye currant of ye water 4 feet;  we may make ye like calculations for greater or lesser swiftnesses of ye water or wind, and for greater or lesser sayls:

  Some have attempted to make horizontal mills wch may turn with all winds;  I have seen of three sorts:

  The first had their sayls concave and convex according to an angle of 45 degrees as is seen in ye figure.  A B is ye height of ye concave, and C D ye height of ye convex, [[blank space of 8 to 10 lines]]
ye wind blowing betwixt these two will not act after ye same manner.  For it will slide on both sides from ye crest C D along ye plains C L and C N, and will not act but as 8 to 5 2/3 whereas incountering ye concave and not being able to slide away it will act by all its force, as if it had a cloth streched upon E Q H F, and so it will act by all ye force of its shoc and as 8 and there being 6 like sayls there would be allways 3 wch would receive somewhat less by one third of ye impulse than ye 3 others wch would necessarily turn ye wheels, but with a little force or else they must be made excessively great, and so they could not be sustained and would be in danger to be carried away by an impetuous wind.

Transcription Notes:
mandc: "3 to 40 feet" is probably a ms error as the Desaguliers translation shows "30 to 40 feet."