588 EXPEEIMENT STATION KECOKD. 



The duty of water, A. McI'iieuson (ForcKinj and Irrip.. 12 {1906), No. 

 'J, pp. Jill-.'{21. pi. 1). — This article gives results of experiiuents made on the 

 experimental farm of the Twin Falls (Idaho) Land and Water Company 

 during lOOti. It was found that the total amount applied on the farm was 

 3G.10 in., whii-li, deducting wastage and an assumed soil evaporation of 28.0(5 

 in. (based en evaiioration from water surface), leaves 5.7 in. as the amount 

 retained by the soil. 



The flooding and furrow methods of irrigation are discussed and the con- 

 clusion reached that the furrow method is the more satisfactory. 



Memorandum dated August, 1875, on the irrigation duty of water and 

 the principles on which its increase depends, J. K. Bkkesforu {Puujuh Irri;/. 

 BraiirJi I'dpcrx. Xo. 10, pp. 1-11). — Notes on the so-called efficiency of canals 

 and a treatment of the nature and theory of absorption and percolation 

 from which it is concluded that the total absorption loss varies as some func- 

 tion of the length of distributary. The theory is advanced, based on observed 

 facts, that more waste of water by absorption occurs in excavated than in 

 embanked channels. The seepage losses from the Ganges canal are said to 

 be "capable of raising the springs over an area of 4.500 square miles to a 

 height of 1.12 ft. in 12 months." 



Note on irrigation duty of the Ban Doab Canal, dated April, 1883, R. G. 

 Kennedy {Pinijah in'iij. Brunch Papvix. So. 10. pp. 12-2')). — Data are given 

 on the rate of absorpti(m of water as determined b.v experiment on a flooded 

 field of loamy soil, from which it was found that the absorption could be 

 expressed i)y the etiuation y =0.0891 x"""^" where y=depth of water over the 

 surface absorbed and x=the number of days under water. The rate of 

 absorption or loss by seepage in case of a canal w'as found to vary from 0.035 

 ft. in depth per houi' over a gravelly open bottom to 0.0070 on the lower silted- 

 up reaches of the canal, the surface upon which such measurements were 

 based being tlie total area of water surface between given jxtints. 



Experiments on gauging the supply entering Rajbahas by means of the 

 headgates (Punjab Irri<j. Branch Papers, No. 8, pp. 20, pis. 2, figs. If). — A 

 series of papers giving the results of observations, the object of which was 

 to determine the coefficient to be used in the usual submerged weir formula 

 when applied in the measurement of water by ordinary lateral headgates. 

 It Avas found that the coefficient varied somewhat with the pressure head 

 and with the width of the gate. For a width of gate of 10 ft. the normal value 

 of coefficient was found to be C=0.79. When the width was other than 10 ft. 

 and not over 12 ft. the coefficient (0.70) is to be nmltiplied by a (luantity 

 ^_ ( 0.7201 +. 0074b) 



^=t* in which b is the width in feet. This modified coeffi- 



7.943 



cient may then be applied in the formula for a submerged weir Q=^C. b. h. 8.02 

 VH, in which h=height of gate opening in feet; lI=working head in feet or the 

 difference between the depth in the canal and in the lateral measured above 

 the sill of the gate, and Q=dischai-ge in cubic feet per second. 



Notched falls, A. G. Reid (Ptinjah Irriy. Branch Papers, No. 2. pp. IS, 

 figs. 3). — A descri]ition of measuring devices "consisting of a vertical wall 

 extending across the channel and of a height above the upstream bed equal to 

 the full supply dei)th in the upstream reach. In this wall one Or more trapezoidal 

 notches are cut from the crest downward through the whole height of the wall 

 to the level of the upstream bed." The notches are of such size as will pass the 

 entire maximum flow without causing the stream to back up. For the deter- 

 mination of flow through such a notch various formuUe are derived, taking into 



