282 EXPERIMENT STATION EECOED. [VoL 37 



cooperation with tlie Office of Public Roads and Rural Engineering of the U. S. 

 Department of Agriculture are reported, which consisted of 317 observations, 

 with 60 different combinations of sizes of orifices, sharp and thiclc edge?^, witli 

 and without gate guides, with and without small bottom contraction, with dif- 

 ferent depths of water in the channel of approach, and with different end con- 

 tractions in the channel of approach and recession. 



The results of the experiments are summarized and a consolidation of the 

 expressions for the exponent and coefficient values of the head, h, " gives the 

 general formula for the discharge through submerged rectangular orifices placed 

 according to the conditions wliich have been taken as the standard : 



fn which Q=the discharge in second-feet; d=depths of orifice in feet; a=area 

 of orifice in square feet ; A=area of cross section of water in channel of ap- 

 proach in square feet; and /i=the difference in feet between the water levels 

 upstream and downstream from the orifice." 



The agreement of the discharge formula with the expeiinieutal data is shown 

 to be within a mean of approximately 0..i i)er cent, with a few individual excep- 

 tion.s which are more than 1 per cent off. 



The standard conditions are taken as follows : 



" The total length of the orifice box is 16 ft. 10 ft. of which forms the channel 

 of approach. Wings set at an angle of 90° are attached to the sides of the 

 upstream end of the orifice box. The floor of the box is level throughout and 

 at the same elevation as the bottom of the canal. The box should be set In the 

 center line of the canal, so as to allow the water to enter the box In straight 

 lines. The sides are parallel and are placed apart a distance equal to the 

 length of the orifice plus 2 ft. 



" Orifices of all sizes have end-contraction distances of 1 ft. The orifice must 

 have sharp sides niul top, and no bottom contraction. . . . The orifice must be 

 placed with its greatest dimension horizontal. If it is desiral)le to use an 

 orific e with bottom contraction, or with wood sides and top, or with gate guides 

 and gate, the discharge tables may be corrected in accordance with the data 

 given. . . . 



" The elevations of the water levels in the channels of approach and recession 

 should he taken in separate stilling boxes, one connection being 5 ft. upstream 

 and the otiier 1.5 ft. downstream from the plane of the orifice. The connections 

 should be through the side of the orifice box about 0.5 ft. above the floor line." 



A few supplemental experiments are also reported. 



The Venturi flume, V. M. Conk (['. S. Dcpt. Apr., Jour. Agr. Research, 9 

 (1917). No. i. pp. 115-129, pis. 4, figs. 8). — "The purpose of this article is to 

 present the fundamenlnl plans and results of preliminary experiments on a 

 new type of device, called the ' Venturi flume,' for measuring water in open 

 channels." 



The flume " consists es.sentially of a flume with a converging and a diverging 

 section and short ' throat ' section between them. The floor, which Is level. 

 Is placed at the elevation of the bottom of the channel in which it Is set. . . . 



"The action of this device depends upon an adaptation or extension of 

 Venturl's principle to the flow of a liquid In an open channel. As water passes 

 through the flume there is a slight surface slope in the converging section, a 

 rather sudden depression In the ' throat ' section, and a rise in the divercring 

 section. The actual loss of head is small. The determination of the flow 



