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66.
[[image: vertical line crossed at the top with a horizontal line labeled A B. The vertical line is divided into sections some solid some dotted line.  The first solid section is B C; then dotted C D (midpoint labeled E; solid line D G; dotted line G H (midpoint [[mis?]]labeled E) probably should be F]]; horizontal lines to left of vertical representing water. Bottom of water designated by a thin single line above a thick dark line]]

A B is ye top of a river retained  C D is an hole of a foot square thro^ wch ye waters ought to go out, let E be ye middle of ye hole and ye height B E of 3 feet. It hath been shown that ye shoc of ye water thrô C D will sustain ye weight of a solid, of water having for base ye square of C D, and ye height E B of 3 feet; that weight shall be therefore 3 times 70 pounds or 210 pounds. Now let ye water be retained so that ye height be 12 feet to F wch is ye middle of ye square hole G H, the spout thru F will go twice as swift as thro E; it therefore as ye diagonal of a square to its side so is C D to G H, ye surface at that hole shall be ye half of that of C D, and there will pass as much water in ye same time because it will go twice as swift, and ye weight wch it will sustain by its shoc shall be equal to ye weight of a solid, wch will have for base ye square of G H and for height F B; but this half solid having its height quadruple to ye first and to it base only less by half, it will [[strikethrough]]]sustain[[/strikethrough]] weigh twice as much; and ye spout G H will sustain a weight double to that wch is sustained by ye spout C D whence is seen that to turn a mill wch wants water, and hath but half ye ordinary , by giving it a quadruple depth ye same water would turn it, and make ye same effect as if it had twice as much water;

Transcription Notes:
mandc: in this script capital "D" looks like a funny lower case "h" and sometimes like a lower cursive "b." From the text it appears that the lower "E" on the diagram should be "F" as water would flow twice as fast through F as through E. See Desaguliers illustration: http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?url=%2Fpermanent%2Flibrary%2FQERNH1MN%2Fpageimg&start=11&mode=imagepath&pn=211&ww=0.0901&wh=0.2925&wx=0.6471&wy=0.3118