Viewing page 111 of 140

This transcription has been completed. Contact us with corrections.

107.

according to the rules it ought to spout to near 17 foot we put another passage of 80 toises lower in ye same conduit wch we made spout alone, and it went but to near 14 foot wch attributed to ye fault of ye passage wch was worse made than ye others.  We afterwards let both ye passages go together and ye spout of ye heighest went but to 12 foot and ye other but to 11 wch shews that a conduit of 5 inches large is not sufficient for a passage of 14 or 15 lines to the height of ye reservatory or for 2 of 10 lines each.  we stopped ye holes and let go ye ordinary spout wch at ye side of ye channel and if elevated 2 or 3 foot heigher at ye same height of ye reservatory than ye last hole, ye reservatory was but 16 foot heigh above ye passage wch was conical and of 12 lines diameter; it spouted about 14 foot instead of a little more than is according to ye rules; wch happened without doubt from ye conical passage as hath been shewn.

  I made other experiments with ye same pipe of 50 foot (wch hath been spoken of) with its vessel on ye top of 1 foot.  We fastened to the bottom an horizontal conduit of ye same largeness of 3 inches and of 40 foot long and we put at ye end a passage of 6 lines, and ye spout went as heigh as when there was but an upright pipe of a foot, ye spout produced also the same effects, viz that after having just spouted to a certain height, it diminished a little about a foot, and ye water being carried to ye bottom of ye vessel ye spout was elevated anew, and went a little heigher than at ye first, and also an horizontal conduit of 4 feet long, and of 3 inches large doth not diminish a spout of 6 lines passage.

  We have found also by experience that a passage of 7 lines went not less heigh than that of 6 lines at a reservatory of 35 foot with a conduit of 3 inches and also that ye pipe of 9 inches might have 52 foot of height for a passage of 6 lines: we may therefore take for a fundamental that a reservatory of 52 foot ought to have a pipe of a conduit of 3 inches diameter when ye passage is of 6 lines, and that ye spout will to ye whole height it ought.

  To compare ye largeness of this conduit to what the reservatory ought to have and ye largeness of ye passages, we shall make this proposition

    As ye number of ye inches which ye spouts give is 
    To ye number of ye inches of another spouts.
    So is ye square of ye diameter of ye conduit of ye first.
    To ye square of ye diameter of ye pipe of the conduit of the second.

  This rule is founded upon this that it is necessary that ye swiftness of ye water running be equal in ye conduits to ye end that there be no more rubbing in one than ye other, now if ye number of inches is quadruple ye surface of ye diameter of ye conduit might be 4 times as great to ye end that ye swiftness if ye pipes be equall:

  Following this rule if we would know what largeness a conduit must be of to have a spout of 100 feet thrô a passage of 12 lines we must take 52 foot height, wch thrô a passage of 6 lines having ye pipe of ye conduit of 3 inches diameter, gives 8 inches and because according to ye table of ye heights of spouts, ye reservatory of a spout of 100 foot ought to be at 133 1/2 foot, we might say as 52 is to 133 so is 64 ye square of 8 to 170, and ye square root of 170 being near 13, we see that ye resrevatory of 133 foot thrô 6 lines will give 13 inches and thrô 12 lines 52 inches of water: therefore as 8 to 52, so 9 is ye square of 3 wch is ye diameter of ye conduit ought to be 58 1/2 of wch ye square root is 7 2/3 near, wch shall be ye diameter of ye conduit sought, but for ye greatest security we may give it 8 inches.

  When ye passages are inequal and ye heights of ye reservatorys equal, we need but make ye diameters of ye conduits in ye same proportion one to another as ye diameters and ye passages: for then ye rubbings would be equal and ye waters will go no swifter would be equal pipes than in ye others, there is an example.