io8 
Journal of Agricultural Research 
Vol. IX, No. 4 
No. 53 and 54 and figures 7 and 8 show the projection of the wood gate 
guides from the bulkhead to have little effect upon the discharge. 
In No. 55 (fig. 9) the wood gate guides were set back a distance of 0.5 
foot, and the resulting discharge was from 4.4 per cent to 6.3 per cent 
greater than the standard. A further comparison of the conditions shown 
in figures 7 and 9 indicate the discharge with the gate guides set back 0.5 
foot to be only about 0.5 per cent greater than that for a plain wood 
orifice without any gate guides. 
A wood orifice, with gate guides set back 0.5 foot and with a wood gate 
slide, as shown in No. 56 (fig. 10), gave a discharge about 8.6 to 8.9 per 
cent greater than the standard. A comparison of No. 56 with No. 55 in¬ 
dicates that the increase due to gate slide alone is from 3 to 4 per cent. 
Complete end contractions on the upstream side of the orifice, and 0.5, 
foot end contractions on the downstream side, with a bottom contraction 
of i^i inches (No. 49), gave a discharge from 2.3 to 2.4 per cent greater 
than that of the standard, and this was about the average increase due to 
the bottom angle-iron contraction with the standard orifice box. There¬ 
fore there was apparently little effect due to the complete end contrac¬ 
tion in the channel of approach; but the decrease which, theoretically, 
should have resulted may have been counterbalanced by the increased 
velocity of approach caused by the smaller end contraction in the channel 
of recession. 
Complete end contractions, both upstream and downstream from the 
orifice, but with an angle-iron bottom contraction of i $4 inches (No. 50), 
caused a deviation from the standard discharge of —0.5 per cent for the 
low head and +2.9 per cent for the high head. The discharge for the 
high head under this condition was therefore about the same as the 
standard size of orifice box with the angle-iron bottom contraction, but 
the increase in end contractions caused a decrease in the discharge for the 
low head of 2 or 3 per cent. The discharge curves represent the experi¬ 
mental data very accurately, and there is no apparent reason for the 
failure to decrease the discharge on the higher heads. 
From the equations for No. 4 to 9 and 13 to 23, inclusive, it will be seen 
that, for a constant depth of water in the channel of approach, and for a 
constant depth of orifice, but for different lengths of orifices, where there 
are three lines in a set, the exponent value is the greatest for the middle 
length. A plot of the three points makes the curve apparent, even 
though the numerical values do not indicate it. The reverse of this curve 
is true for the coefficient values, as is shown by the several conditions of 
contraction, when comparable conditions are inspected. A similar com¬ 
parison for No. 35 to 44, which are with bottom angle-iron contraction, 
shows both the coefficient and exponent value for the middle length to be 
the lowest. Therefore the insertion of the angle-iron bottom contraction 
seems to have reversed the curve for the law of the exponents, but pro¬ 
duced no change in the curve for the coefficients. 
