333 NOTES ON DOCKS AND DOCK CONSTRUCTION, 



height of 55 feet. The suction-pipe is 20 inches diameter, and 

 terminates in a strainer 3 feet 6 inches diameter. The suction- 

 pipe and strainer rest on the bottom of the well, and serve to 

 support the weight of the valve-boxes. 



Temporary Pumping. The quantity of water likely to be 

 met with in carrying out a large dock-work is always more or 

 less problematical, and may be made up of natural drainage, 

 rainfall, and leaks from the sea or other outside waters. 



Local conditions and personal bias must always play an 

 important part in the choice of appliances. It may, however, be 

 taken as a maxim that for all temporary purposes the more 

 simple the arrangement the better. Pumps, and engines for 

 driving them, of a complicated construction, and requiring 

 elaborate and costly foundations and high-classed skilled 

 attention, are altogether out of place < 



It is wise to concentrate the pumping as much as possible. 

 If on a work of moderate size, to one or two points ; or if on a 

 large work, by districts. There will of course be exceptions to 

 this rule ; but isolated pumping-places should be reduced as 

 much as possible. 



The sumps should be well below the deepest permanent 

 works. On the power to keep the water down a few inches 

 extra for a short time may depend the success of some important 

 part of a work. 



The capacity of the pumps and driving power should be in 

 excess of the actual requirements. To continuously work up to 

 full power is false economy, and leaves no margin for con- 

 tingencies. 



The pumping appliances should be in duplicate, or divided 

 in such a manner that any breakdown may not affect the whole. 

 It must be borne in mind that pumping-gear and boilers cannot 

 be expected to run satisfactorily without occasional stoppages 

 for cleaning and adjustment. Accidents to pumps, engines, and 

 boilers will happen at the most unexpected times, and when 

 they certainly should not happen according to paper arrange- 

 ments. If at such times duplicate pumping power is n<>t 

 available, stoppage of the works may result, possibly with very 

 serious consequences. 



