The theory and practice of surveying. Designed for the use of surveyors and engineers generally, but especially for the use of students in engineering (1886)
Johnson, J. B. (John Butler), 1850-1902 · New York, J. Wiley & sons · leaf 330
Fig. 74. much as twenty per cent in their times of passage, showinggreat irregularity in the velocity of different parts of the samefilament. This is due to Internal movements in the water,such as boils, eddies, etc. It is for this reason that greatrefinement in such observations Is useless. A… … I IG. 75. gives only the velocity of a given small volume of water whichsurrounds the lower float, while a current-meter observation,as will be seen, gives the mean velocity of a given filament of 300 SURVEYING. the stream of any required length. And as different portionsof the same filament have…
Surveying
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