The practice of engineering field work, applied to land, hydrographic and hydraulic surveying and levelling, 2권

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70 페이지 - The ordinary rectangular notches, accurately experimented on as they have been, at great cost and with high scientific skill, in various countries, with the view of determining the necessary formulas and coefficients, for their application in practice, are for many purposes suitable and convenient. They are, however, but ill adapted for the measurement of very variable quantities of water, such as commonly occur to the engineer to be gauged in rivers and streams. If the rectangular notch is to be...
72 페이지 - ... the two planes slanting upwards from their intersection more gently than the sides of the notch. The level floor, although theoretically not quite so perfect as the floor of two planes, would probably for most practical purposes prove the more convenient arrangement. " With reference to the use of the floor it may be said, in short, that by a due arrangement of the notch and the floor a discharge orifice and channel of approach may be produced, of which (the upper surface of the water being considered...
71 페이지 - ... on the flow of the water to the notch. If it were practicable to dam up the river so deep that the water would flow through the notch as if coming from a reservoir of still water, the difficulty would not arise. This, however, can seldom be done in practice, and although the bottom of the river may be so far below the crest as to produce but little effect on the flow of the water when the quantity flowing is small, yet when the quantity becomes great, the velocity of approach...
71 페이지 - ... may be accurately gauged by their flow through the same notch. The reason of this is obvious from considering that, in the triangular notch, when the quantity flowing is very small, the flow is confined to a small space admitting of accurate measurement ; and that the space for the flow of...
71 페이지 - Further, the ordinary rectangular notch, when applied for the gauging of rivers, is subject to a serious objection from the difficulty, or impossibility, of properly taking into account the influence of the bottom of the river on the flow of the water to the notch. If it were practicable to dam up the river so...
71 페이지 - ... so as to form a bottom to the channel of approach, which will both be smooth and will serve as the lower bounding surface of a passage of approach, unchanging in form, while increasing in magnitude at the places, at least, which are adjacent to the vertex of the notch. The floor may...
71 페이지 - In the notches now proposed, of triangular form, the influence of the bottom may be rendered definite, and such as to affect alike (or, at least, by some law that may be readily determined by experiment) the flow of the water when very small, or when very great, in the same notch.
151 페이지 - ... its well-formed brother. The two placentae removed by Dr Edmondsou were probably the partly united halves of a single afterbirth. In the peculiar relations and arrangement of the umbilical vessels it is very probable that the cause of the deformities that existed in this twin...
73 페이지 - This formula is submitted, at present temporarily, as being accurate enough for use for ordinary practical purposes for the measurement of water by notches similar to the one experimented on, and for quantities of water limited to nearly the same range as those in the experiments ; but as being, of course, subject to amendment by more perfect experiments extending through a wider range of quantities of water.
72 페이지 - ... whatever may be the result in this respect, the main object must be to obtain for a moderate number of triangular notches of different forms, and both with and without floors at the passage of approach, the necessary coefficients for the various forms of notches and approaches selected, and for various depths in any one of them, so as to allow of water being gauged for practical purposes when in future convenient, by means of similarly formed notches and approaches. The utility of the proposed...

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