LOCAL ENGINEERING WORKS. 109 



and the question remains in suspense until this has taken 

 place. I must refer to the Report itself for a detailed state- 

 ment of the case, only quoting the summary on its last page. 



" 1st. The proposed Black-Rock Culvert is necessary in 

 order entirely to prevent flooding during periods of exces- 

 sive rainfall, such as in March, 1889, especially when coupled 

 with adverse conditions of tides. 



'' 2nd. It would certainly he effectual in its operation. 



'^ 3rd. It is also the best scheme for the prevention of 

 floods. 



" 4th. It can be efficiently carried out for the amount 

 of the Parliamentary Estimates." 



If it be conceded that the improved channel of the 

 Frome will convey six million cube feet per hour and no 

 more, without causing floods, the whole question of the 

 necessity for a relief culvert obviously hinges on the esti- 

 mated amount of rainfall within a limited time, and the 

 amount of flood water due to such rainfall which would pass 

 down the Frome. There is also another important considera- 

 tion connected with the capacity of the Floating Harbour 

 referred to later on. Mr. Howard and Mr. Martin, in their 

 Reports, estimated the maximum flood discharge of the Frome 

 at eight million cube feet per hour. This was in 1881 and 

 1882, since which the passage of flood-water has been accele- 

 rated by the removal of mills and other obstructions in the 

 upper part of the Frome basin. Mr. Hawksley and Mr. 

 Harrison Hayter, in their evidence^ before the Lords' Com- 

 mittee of 1890, estimated the rainfall at 3|- inches in twenty- 

 four hours, yielding eighteen to twenty-one million cube feet 

 per hoar. The late Dr. Burder, in a paper read before the 

 Naturalists' Society last session, gave a much less estimate. 

 My own estimate was nine to ten million cube feet per hour ; 

 and the maximum of twelve million cube feet per hour was 



I 



