CHAP. III.] 



PUMPS. 



55 



kind, hydraulic wheels being used. At the present time, the new 

 wheels, only four in number, and each setting in action four horizontal 

 pumps, furnish a quantity of water much greater than that given by 

 the old machine. This may serve to give an idea of the perfection 

 now arrived at in mechanical constructions during the last two 

 centuries. The Chaillot pumps are moved by steam. A steam- 

 engine, established 100 metres from the banks of the Seine, also 

 works the pumps supplying water to the town of Fontainebleau. The 

 immense draining works undertaken in Holland have been a long 



FIG. 37. The new water-wheels and pumps at Marly. 



time worked by pumps, with wind for motive power. In 1840, more 

 than 2,500 windmills were still used for this purpose. At the same 

 time the draining of the Lake of Haarlem was undertaken with the 

 help of a steam-engine of 350-horse power, which worked eleven 

 pumps. The mean clearing was 475,000 cubic metres every twenty- 

 four hours. 1 



1 For more details on works of this kind, undertaken by the aid of pumps or 

 other similar machines, the interesting work of the Bibliotheque des Merveilles, on 

 Hydraulics, by M. Marzy, may be consulted. 



