ENGINEERING CONSTRUCTION AND RAINFALL. LXIX. 



of catchment, and co-efficient of discharge. The kernel of the 

 whole question of discharge from catchments had been, in his 

 opinion, entirely overlooked — viz , the duration of the rainfall, 

 and its effects, both as regards intensity of precipitation and area 

 affected. The period of maximum flow at the outlet of any 

 drainage area during the progress of a rain-storm occurred when 

 the flood waters from the remotest confines of the catchment, as 

 well as those from the nearer slopes, were reaching the outlet at 

 the same moment. The duration should be proportional to the 

 distance of the outlet from the confines of the catchment. The 

 paper was unsatisfactory in this respect — that, while the author 

 thoroughly reviewed the question, he came to no definite 

 conclusion. 



Prof. Warren thought that the use of a formula, expressing 

 the law of flow in so far as it depends on the area and the rain- 

 fall, was desirable in estimating the discharge from a catchment, 

 as the judgment of the engineer had then only to be applied to 

 the determination of the co-efficient in the formula. The result 

 would then be as correct as could be expected from the nature of 

 the problem, and more correct than would be obtained by 

 attempting to exercise the judgment on all the factors of the 

 problem combined, i.e., by guessing the size of the waterway. 

 The formulae of Dickens, Kernot, and Biirkli-Ziegler were 

 identical, in so far that they each made the area of the opening, 

 or the discharge, proportional to the three-fourths power of the 

 area; but in the Biirkli-Ziegler formula, the engineer was 

 enabled to exercise his judgment more in detail, and thus obtain 

 more accurate results. The intensity of rainfall on areas of 

 various sizes, and the time necessary for it to flow from the more 

 remote portions of the catchment had been dealt with by Mr. 

 Chamier. He agreed with the general remarks on rainfall made 

 by Mr. Chamier, but he disagreed altogether with his method of 

 introducing it into a formula. If, for example, 6 inches of rain 

 fell on a catchment in six hours, and it took 12 hours for the 

 rain falling on the most remote portions of the catchment to 

 reach the outlet, then he saw no objection in a problem of this 



