RURAL ENGINEERING. 685 



water passed. More water is passed per revolution on lower rates of discliurge. 

 Tlie tests show that the meter will probably register within 2.5 per cent of the 

 true quantity. The fall required in the ditch varies with the rate of flow from 

 about 1 in. for a discharge of 3 second-feet to 4 in. for a discharge of 5 second- 

 feet. The high cost of this meter is said to be against its general use. 



The IIlll meter consists of a circular horizontal opening in the floor of a box 

 through which the water to be measured is made to pass. The meter consists 

 of curved vanes on a central drum. It sits in the center of the opening and is 

 turned by the water as it strikes against the vanes on rising through the open- 

 ing. The turning of the meter drives the gears of a counting device which 

 records the water passed in acre-feet. Tests of a 12-in. Hill meter showed that 

 this size of meter apparently registers the quantity passed within 1.5 per cent 

 for discharges of from 1 to 3.5 second-feet. For discharges of less than 1 .second- 

 foot more water passed the meter than was registered and for discharges of 

 3.5 second-feet the water boiled up through the opening so as to submerge tlie 

 counter. The loss of head of fall in the water required for this meter varied 

 from 1 in. when carrying 1 second-foot to 6^ in. when carrying 3.5 second-feet. 

 "The Hill meter seems adapted to use under the usual conditions of irrigation 

 practice. It is simple and has few^ wearing parts. The head required for the 

 different sizes is less than that needed for the use of weirs. The record of the 

 total quantity of w'ater passed can be read in units of 0.001 acre-foot." 



The data of the tests are given in an appendix. 



Stream gag'ing by titration: Comparative tests of new chemical and stand- 

 ard miechauical methods of gaging stream flow, L. W. Collkt et al., trans. 

 by G. Blaauw and R. E. Ward {Engin. and Contract., 42 (Wl-'f), No. 12, pp. 

 270-273, figs. 3). — This article explains the method of stream gaging by chemi- 

 cal means, describes the preparation of the solution, and the computation of 

 results. 



The process is based on the theory that if a constant quantity of concentrated 

 solution of sodium •clorid be injected into a stream and samples of water taken 

 at a certain distance from the poiBt of injection into the stream, the discharge 

 may be determined by the fact that the ratio of the discharge of the initial 

 solution to the discharge of the final solution is inversely proportional to the 

 ratio of their concentration. The conditions necessary for the success of this 

 method of gaging are (1) a constant rate of flow of the initial solution, (2) 

 perfect mixing, and (3) accurate titi'ation of the salt solution. 



Comparative tests made in Switzerland of the chemical method with the cur- 

 rent metei*, curtain, and weir methods are described, from which it is concluded 

 that the titration method is rapid and exact, permits the easy determination 

 of a discharge of high head turbines, is applicable in certain cases to test low 

 head turbines, and may be used in gaging Alpine streams whore otlicr methods 

 are considered inaccurate. 



The hydraulics of irrigation, drainage, and other channels, L. Schmeeb 

 {Engin. and Contract., 42 {1914), No. 13, pp. 284-290, figs. 4).— The author 

 briefly reviews the history of channel flow formulas, deduces an equation for 

 circular conduits running full, discusses the practical application of formulas 

 for conduits under pressure, and deals in more or less detail with formulas 

 governing the flow of water in open conduits, covered aqueducts, and egg-shaped 

 conduits. 



Ground-water supplies, O. Smreker (Dns Grundivasser, Seine Erscheinungs- 

 fornien, Bcwcgung.'igcsctzc, und Mcngenbestivimung. Leipsic: W. Engelmann, 

 1914. PP- 67, figs. 27; rev. in Engin. News, 72 (.1914), No. 21, p. IO46).— This 

 book is divided into seven sections which embrace a review of the principal 



