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61.

[[image: three dimensional drawing: there is a horizontal tubular object A B which appears to have a dowel inserted longitudinally through its center and sticking out each end, labeled a b c d at the right end.  Inserted through the tube horizontally at 90 degrees is a plank G H with a weight R poised on the plank at H. Directly above G H is a vertical plank L I labeled Q.  Near the left end of and at about a 45 degree angle to G H and to A B's axis is a plane figure (rectangle) M N O P vertical to A B labeled S.]]

axis as ye point Q, it cannot sustain ye weight R, because its direction will not be parallel to ye direction of ye extremity of ye rule I L, and it can sustain but a weight wch shall be to ye weight R as ye side of a square is to its diagonal, and if ye same spout is parallel to ye axis A B and strikes at ye same point S, it will be yet needfull to diminish ye weight R in ye same proportion to make an equilibrium, because that that spout will strike ye rule obliquely at angle of 45 degrees, and then ye weight R shall have but half of its weight:  For if A B C D is a square, ye first proportion shall be of A C to A B, and ye second as of A B to A E ye half of A C as it is explained more at large in ye treatise of percussion at ye end of ye 13 proposition of ye second part:  Now ye wind wch strikes ye sayls of a windmill strikes ye obliquely and if it should incounter each sayl under an angle of 45 degrees, there would remain to it of its force but according to ye proportion of ye diagonall of a square to its side by that only cause:  But if that sayl which is obliquely at ye axis was according to ye same angle;  that second cause would diminish also ye force of ye wind according to ye same proportion, as hath been said of a spout of water, and ye total diminution by these 2 causes should be half of ye force of ye wind when it shocs ye rule directly, as IL disposed to be moved at ye beginning according to its direction, so that if its whole force was 80 it would be reduced to 40 by these two causes.  But because that ye sayl whose obliquity is 45 degrees receivs something less of ye wind than when it is directly opposed, it would receive yet a third diminution according to ye same proportion of A C to A B and ye whole diminution shall be as A C to E F or near as to 80 to 28 1/4.  But if ye obliquety of ye sayl is N O and ye angle of A B and N O be 60 degrees, then ye first cause alone will diminish half ye force of ye wind and will reduce it from 80 to 40 and if two others together will reduce it from 40 to 31 near;  whence we may judge that it is better that ye sayls of mills have that obliquity than that of 45:

[[image:  Square A B C D with diagonal lines A C and B D intersecting at E with a line from E up to F at the midpoint of A B]]

  To know ye force of a wind wch should shoc directly ye sayl of a vessel, we must know ye swiftness of ye wind:  It is found by permitting it to carry away a light down [[feather]] from a 

Transcription Notes:
mandc: reviewed and amended image descriptions. I put a space between letter-labeled point (A B, N O) to avoid appearing as a word. Image: http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?url=%2Fpermanent%2Flibrary%2FQERNH1MN%2Fpageimg&start=11&viewMode=image&mode=imagepath&pn=211&ww=0.1993&wh=0.2736&wx=0.6203&wy=0.0423