Drainage by Gravitation. 35 



length, and 3 feet 6 inches in diameter- They were put into 

 action by exhausting the air from the inside by an air-pump 

 worked by a 10 horse-power steam engine. These syphons 

 continued in use for 15 years. Owing to their capacity 

 not being sufficient to cope with heavy floods and to dis- 

 charge the water with sufficient rapidity, there was frequently 

 a difference of more than 4 feet between the level of the water 

 in the drain and that in the river, the average varying from 

 2 to 3 feet, a very serious loss in such a flat district It being 

 found that the cost of adding a sufficient number of syphons 

 to drain the fens effectually would be greater than that of 

 building a new sluice. Sir J, Hawkshaw reluctantly advised 

 the latter course, although contending that the syphons were 

 right in principle and practice. 



D 2 



