92 The Drainage of Fens and Low Lands. 



CHAPTER VIL 



CENTRIFUGAL PUMPS. 



In giving the following description of the centrifugal pump, 

 the subject has been confined, as far as practicable, to pumps 

 with low lifts adapted for drainage purposes. 



Although the principle of the centrifugal pump was known 

 more than one hundred years ago, and pumps of this descrip- 

 tion were made and used experimentally fifty years since, 

 it was not until the Exhibitioa of 1851 that they were 

 brought into prominent notice. At the British Association 

 meeting held at Birmingham in 1849, Mr. J. G. Appold ex- 

 hibited a model of a centrifugal pump. After that, by an 

 exhaustive set of experiments, principally directed as to the 

 best form for the fans, Mr. Appold gradually improved the 

 discharging capacity, and was enabled to exhibit a pump at 

 the Exhibition of 1851 which formed one of the chief features 

 of interest, the public being astonished at the immense volume 

 of water put in motion by a machine which appeared, both 

 from its size and simplicity of form, to be quite inadequate to 

 the result attained. 



Practically the form of pump shown at the Exhibition is the 

 pump of the present day, no material alteration having been 

 since effected Although the general principle on which the 

 pump acts is simple, the determining of the proportion of the 

 different parts, and of the effect of the shape of the fan, is 

 extremely difficult, requiring complex calculations, the data 

 for which are so scanty as to render them not to be relied on 

 unless checked by actual experiment. 



Centrifugal pumps were "*first brought into use for the 



