50 The Drainage of Fens and Low Lands. 



CHAPTER IV. 



DRAINAGE BY STEAM POWER. 



Machines for Raising Water. — The machine for effi- 

 ciently draining low lands is one that will readily adapt 

 itself to the varying amount of work to be done, owing to 

 increase or decrease of lift from the rise and fall of the tide, 

 or of floods in the outfall into which it discharges, and from 

 the lowering of the water in the feeding drain as pumping 

 proceeds. The parts should be as simple as possible, and the 

 machine should be so constructed as not to get out of order 

 from lying by. Owing to the intermittent character of the 

 work, most pumps are idle for the greater part of the year. 



Setting aside special contrivances which have occasionally 

 been used, but, owing to their unsuitability, the use of which 

 has not been repeated, the machines used for raising water for 

 the drainage of land are scoop wheels, screw pumps, bucket 

 pumps, and centrifugal pumps. Of these the scoop wheel and 

 Archimedean screw pump are the oldest types of machine. The 

 former still does duty to a greater extent than any other 

 method of raising water for drainage purposes, although it is 

 gradually being superseded by the centrifugal pump. Archi- 

 medean screw pumps have not been adopted in this country, 

 but in Holland they have been largely employed. 



Bucket pumps have been used in some instances, both in Hol- 

 land and England, for land drainage, notably for the drainage 

 of Lake Haarlem, a full description of which will be found 

 later on. Bucket pumps are still in use for the drainage of 

 the Waldersea district on the Nene and of the Marton district 

 on the Trent The use of these pumps was probably advised 



