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114.

[[image:  drawing of a barbell-shaped object with opposite ends labeled A and B, the bar connecting them C D, and a line in the center of the bar H.]]

[[image:  drawing of a cross section of a wall with a beam E F extending from point G to the right, with a weight I suspended from F.]]

  To know if experience was agreeable to this reasoning, I caused two sticks of very dry wood to be turned one of them represented by A B had at its ends two small bowls, and ye rest C D was uniformly of three lines thick, ye other E F was thrô out its whole length 3 lines thick:  I put ye end of this half to ye point G into a small hole made in a beam and it filled it exactly, and I tyed at ye other end, a weight of 6 pounds in F this distance GF was 4 inches or 48 lines, and by consequence was 48 times greater than 1/3 of ye thickness of ye cylindricall stick G F, since 1/3 was but as one line and according to Galileus ye proportion of ye weight was augmented 32 times but ye stick was a little bent and ye distance was but as 30 to 1 near, ye weight I being six pounds suspended at ye point F broke ye stick at ye point G:  Now if ye force of this weight was augmented by 30 times it ought to make an effort but 180 pounds ye product of 30 by 6.  I afterwards suspended ye stick A B by 4 cords tyed to a small cord wch went twice round ye neck D, and was retained by ye bowl B D and I fitted after ye same manner 4 other cords to ye bowl C A to suspend a weight of 180 pounds wch ought to break ye stick A B if Galileus' rule were true;  but it did not break.  Ye experiment was made in ye presence of Mr Carcary, Roberral and Hugens, I added weight of 10 or 12 pounds one after another, and at last when there was in all about 330 pounds, it broke in ye point H.  Now if we take ye proportion of 47 to 1 (wch is 1/3 of ye thickness) because ye stick did bend a little before it broke, ye product of 47 by 6 is 282 instead of 330 but it seems that if we had only put 300 pounds and let them lye there some time as we did ye 6 pounds upon I, it would have broek, likewise, but lastly ye proportion was greater than of 30 to 1, wch might happen because that ye stick G F was either weaker towards ye point G or a little thicker:  We reiterated ye experiment leaving a greater thickness at ye two ends of ye stick E F, leaving only two inches from G towards F that that part may bend itselfe very little.  I made use afterwards of some canes of solid glass of 3/4 of a line thickness and I found always that we must take near ye proportion of ye length of ye glass cylinder to one third of its thickness and in an experiment where according to Galileus there needed but 30 pounds to break ye small glass rod situated perpendicularly it was necessary to suspend 50;  Mr Hubin fitted ye small bowls of glass to two ends of a cylinder to suspend it.

  It may be objected that if wood, glass or metalls there is nothing to be extended before a fraction;  I confess that ye extension of glass is not sensible;  but that of metalls is easyly known in that ye cords of musical instruments of any metal are sensibly extended whence it follows that a cylinder of an inch thick ought to be extended also, but there is need of above 2000 pound weight to extend it, sensibly for since a bowl of glass and steel is sunk by ye shoc, and returns into its first figure it may be extended also.  If we let fall a cylinder of dry wood of an inch thickness upon a plate stone, it will rebound, and by consequence hath a spring, and its parts suffer extension and compression;  and because experience shows that a small stick that is bended to be broken is shortened towards ye concavity of its curve;  it is necessaryly extended towards ye convexity before it is broken:  Whence we may conclude that it makes an effort to break ye compression towards the concavity.

Transcription Notes:
mandc: Reviewed and amended image descriptions, changed J's to I's. "Hugens" probably Christiaan Huygens (1629-1695), FRS was a Dutch physicist, mathematician, astronomer and inventor, who is widely regarded as one of the greatest scientists of all time and a major figure in the scientific revolution. The Hugens reference would seem to confirm mid 17th C. Image: http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?url=/permanent/library/QERNH1MN/pageimg&viewMode=images&mode=imagepath&pn=336&ww=0.1931&wh=0.0652&wx=0.4898&wy=0.1434