150 Transactions of the Royal Society of Victoria. 



enquiry held on the Cootamundra disaster, where five 

 engineers gave different opinions — one said the culvert was 

 not sufficient to take J inch of rain in 24 hours, and another 

 said it would take 28 inches of rain in 24 hours. Matters 

 being thus, I need no other excuse for referring to this 

 subject. 



Mr. Beardmore, in his Manual of Hydrology, has devoted 

 a section to discharge from rivers, and gives a list from 

 many sources. Mr. L. de A. Jackson in his Hydraulic 

 Manual, devotes a space to it. Mr. Neville in his work also 

 devotes a space to it. 



As a preliminary to the subject, I submitted a paper to 

 this Society, Notes on Hydrology, in June 1883. In June 

 1885, in Section A, I also submitted a paper on Rainfall 

 and Flood Discharge, and with the hope of preparing a 

 paper worthy of submitting here, I posted more than 150 

 circulars to engineers, but failed to elicit any data. I have, 

 therefore, to submit this paper, bald as it is, with the hope 

 that other information may be supplied by those who may 

 have had better opportunities for observing. I claim a 

 little indulgence for introducing matters of an elementary 

 character with the data I submit. 



The amount of discharge depends on many circumstances. 

 The amout of rain ; size of area, especially the nature of the 

 area varying from rock to beds of sand ; the form of the 

 area ; inclination of surface, whether dry or soaked. I 

 propose only to deal with the maximum discharge, and that 

 due to the rainfall only ; the maximum discharge depends 

 on the maximum rainfall. 



The rainfall has been observed as to the total daily fall 

 in many places, but the same attention has not been paid to 

 the amount in times of short duration (B), and the area 

 over which that rain falls. We have records such as an 

 inch in fifteen minutes, but no evidence of the extent of 

 such rains. The maximum dischai^ge must take place from 

 any watershed, when with the maximum rainfall over the 

 whole area, it has continued long enough for a drop from 

 the extreme distance to join drops fr^om the whole of the 

 area at the outlet. Hence the time the water takes to 

 travel the longest distance must be an element in the 

 discharge, and we must approximate the rain which falls in 

 that time. Supposing it to be such a length as to take an 

 hour to travel, we must approximate the rain — suppose it 

 an inch. 



