. Better fruit. Fruit-culture. Page 10 BETTER FRUIT December, ipip crest of the rectangular or trapezoidal weir, or witli the vertex of tiie trian- gular weir. If an open weir pond of sufficient width is used the scale, or a lug upon which to place a rule, may. Fig. 4. TrinngLihir notch weir. be fastened to the bulkhead at a lateral distance from the end of the notch of not less than twice the greatest depth of water "H" over the crest. To get the zero point of the scale or the lug level with the crest, a carpenter's level and straight edge or a surveyor's level must be used. Allowin
. Better fruit. Fruit-culture. Page 10 BETTER FRUIT December, ipip crest of the rectangular or trapezoidal weir, or witli the vertex of tiie trian- gular weir. If an open weir pond of sufficient width is used the scale, or a lug upon which to place a rule, may. Fig. 4. TrinngLihir notch weir. be fastened to the bulkhead at a lateral distance from the end of the notch of not less than twice the greatest depth of water "H" over the crest. To get the zero point of the scale or the lug level with the crest, a carpenter's level and straight edge or a surveyor's level must be used. Allowing the water to flow into the pond and slowly rise till it flows over the ^vei^ crest is in- accurate, since the water surface will rise appreciably above the crest before flow over the crest begins. Small er- rors in reading "H" causes relatively large errors in the discharge determi- nation. Rectangular Weir.—The rectangular weir, named from the shape of its notch, is the oldest weir in use. Its simplicity of form, ease of construc- tion and accuracy make it a desirable device for measuring water. Because of the vertical ends and the complete end contractions the middle part of the weir discharges more water than the same length of weir near either end, whereas the trapezoidal weir with sloping ends is commonly believed to discharge the same amount of water near either end as it does in the middle. However, extensive ex- periments conducted by the United States Department of Agriculture indi- cate that four times the discharge over a 1-foot trapezoidal weir is greater than the discharge under the same head over a 4-foot trapezoidal weir. Ninety - Degree (90°) Triangular Notch Weirs.—The triangular notch weir is especially adapted to the meas- urement of small quantities of water, varying from a very small fraction of a second-foot to 2 or 3 second-feet. Cone has demonstrated that very small crest lengths in the rectangular and trapezoidal weir, e. g. K' foot, do
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