The art of paper-making : a guide to the theory and practice of the manufacture of paper : being a compilation from the best known French, German and American writers by Unknown

Author:Unknown
Language: eng
Format: epub, pdf
Publisher: London : Kent & Co.
Published: 1874-03-25T05:00:00+00:00

134 AVASIIING-AVATER, WATER PO^YER, STEAM BOILERS, ETC.

straight banks and as even a width as can be found, should be selected. Measure of it a certain length, say 100 feet, and in several points of this length the vertical section, viz. its width and medium depth. From these several ones the medium size of a section is calculated.

An instrument, resembling a wind-mill on a small scale, has been constructed for the measurement of the velocity of flowing waters, which, when set in a stream at any point, registers the number of revolutions of a fan, which enables us to obtain the speed.

If such an instrument is not to be had, a piece of light wood may be used in its place ; it is simply thrown into the middle of the stream,at the point above where the measured part begins, while the time ^vhich it consumes in flowing down through the 100 feet length is obseiTedwith a watch. The number of feet made by it in one second is the velocity, and gives, multiplied by the number of square feet of the medium vertical section, the number of cubic feet of Avater which pass through the stream in one second.

If a precise calculation is to be made, the speed on the surface cannot be accepted as that of the whole body of water. The friction on the bottom and sides retards the motion, and must be taken into account. If we call the surface velocity per second, found with the floating wood V, the real velocity v of the stream is expressed, according to the best authorities, by the formula—

7-71 + V

v = V

10-25 + V

If we have, for example, a race or stream of 20 feet medium width, 3 feet medium depth, with a surface

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