86 Book of Steamships 



clog the boilers. Before surface condensa- 

 tion was brought about the sea-water used 

 for condensing it, and eventually the con- 

 densed water, which was, of course, dis- 

 tilled water, was mixed with that from 

 the sea, and pumped back into the boilers. 

 In surface condensation currents of cold 

 sea-water are forced through numerous 

 small pipes, and the steam is brought into 

 contact with the exterior of these pipes. 



The sea-water having done its office is 

 returned to the ocean again. Those of you 

 who have been puzzled by the gallons of 

 water which seem to be issuing to waste 

 from pipes at the sides of a steamer, will 

 realise now that these pipes are the out- 

 lets of the condenser. The distilled water 

 obtained in the process of condensation is 

 pumped back to the boilers, and so, in 

 effect, is used over and over again. Here 

 we find a great economy, but there was 

 a greater on the way. This was the intro- 

 duction of compound engines. 



I need not here go over familiar ground 



