BRINE-PUMPS. 



engineer. The injurious consequences are thus prevented which 

 sometimes ensue, when the blow-off cocks are left open by any 

 neglect on the part of the engineer. When it is necessary to blow 

 off, the engineer moves the lever H to the position D'. The pres- 

 sure of the steam in the boiler on the surface of the water 

 forces the salted water or brine up the pipe B A, and through the 

 open cock c into the tank, and this continues until the tank is 

 filled : when that takes place, the lever is moved from the posi- 

 tion D' to the position F', by which the cock D is closed, and the 

 cock F opened. The water in the tank flows through the pipe E 

 into the sea, air being admitted through the valve v, placed at 

 the top of the tank, opening inwards. A second ton of brine 

 is discharged by moving the lever back to the position D', and 

 subsequently returning it to the position F' ; and in this way the 

 brine is discharged ton by ton, until the supply of water from the 

 feed which replaces it has caused both the balls in the indicator to 

 sink to the bottom. 



39. A different method of preserving the requisite freshness of 

 the water in the boiler was adopted by Messrs. Maudslay and 

 Field. Pumps called Irine-pumps are put into communication 

 with the lower part of the boiler, and so constructed as to draw 

 the brine therefrom, and drive it into the sea. These brine- 

 pumps are worked by the engine, and their operation is constant. 

 The feed-pumps are likewise worked by the engine, and they bear 

 such a proportion to the brine-pumps that the quantity of salt 

 discharged in a given time in the brine is equal to the quantity 

 of salt introduced in solution by the water of the feed-pumps. 

 By this means the same actual quantity of salt is constantly 

 maintained in the boiler, and consequently the strength of the 

 solution remains invariable. If the brine discharged by the 

 brine-pumps contains ^ parts of salt, while the water introduced 

 by the feed-pumps contains only i part, then it is evident that 

 five cubic feet of the feeding- water will contain no more salt than 

 is contained in one cubic foot of brine. Under such circumstances 

 the brine-pumps would be so constructed as to discharge | of the 

 water introduced by the feed-pumps, so that f of all the water 

 introduced into the boiler would be evaporated, and rendered 

 available for working the engine. 



To save the heat of the brine, a method has been adopted in 

 the marine engines constructed by Messrs. Maudslay and Field, 

 similar to one which has been long practised in steam-boilers, and 

 in various apparatus for the warming of buildings. The current 

 of heated brine is conducted from the boiler through a tube 

 which is contained in another, through which the feed is intro- 

 duced. The warm current of brine, therefore, as it passes out, 



141 



