Publisher's Synopsis
Excerpt from The Journal of the Franklin Institute, Vol. 118: Devoted to Science and the Mechanic Arts; Nos. 703 708; July to December, 1884
As the Perkiomen division is the most extensive, my instructions were to make a beginning on that side, and accordingly explorations and surveys of all those streams were immediately begun in order to establish gauging points.
It was proposed at first to use as far as possible current meters for gauging, but investigation showed that little could be done to advan tage with those instruments under the ordinary conditions of the sum mer ?ow of the streams. These natural channels are very rough and of considerable width, showing everywhere the marks of the high ?ows of the winter and spring months, and the inclination of their beds are, as a rule, considerable, the streams forming, in most cases, _a constant succession of mill-ponds, with but short intervals between each dam and the head of the succeeding pond below. Besides, the extreme shallowness of all the streams in their normal summer condition ren dered the use of the current meter impossible at points where there was a perceptible current.
Accordingly it was decided to build a number of low weirs or dams, and to measure the ?ow passing them. This method offered the advantage that the manner of observation is simple, taking but little time, and affording opportunities for continuous measurements when ever desired. The weirs were intended to gauge the ordinary summer or low ?ows, and the meters were to be used whenever the streams were too high to allow the weirs to act as such.
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