272 



OF THE REGULATION AND 



[SECT. vin. 



six parts ; l consequently, if the boiler contain one hundred parts of water, and * 

 parts be used for steam, and n parts let out, fix on the degree of saturation, 

 for example, to contain a parts of saline matter ; then if 3 ( s + n) = a n, the 

 quantity of salt entering and the quantity quitting in the same time will be equal ; 

 hence, 



a-3- 



If a = 30, the water in the boiler will not reach to a higher degree of saturation 

 when a ninth part of the quantity used for steam is allowed to escape. Hence, as 

 it requires only about one-sixth of the quantity of fuel to boil water that is required 

 to convert it into steam, the loss of fuel will be $ x $ = one fifty-fourth part. 2 



566. OF WORKING A CONDENSING ENGINE. The engine is supposed to be at 

 rest, the cylinder quite cold, and the condenser partially filled with water, and the 

 piston at the top. When the water in the boiler begins to boil, let steam enter by 

 the valves, or the slide, and the communication which is added when a slide is 

 used ; it will then fill the cylinder and pipes; and the injection cock being shut, it 

 will gradually displace the water in the condenser, 3 by forcing it out at the blow 



1 According to Mr. Faraday's experiments, the deposits take place at the following degrees of 

 saturation and temperature, when 1000 parts of sea water were reduced by evaporation. 



- An ingenious combination was formed by Messrs. Maudslay and Field, to avoid this loss, by 

 causing the water entering the boiler to traverse the central parts of the pipe which removed the 

 saturated hot water ; the loss of effect then becomes very small, even when the degree of satura- 

 tion is much less. Now to prevent the deposition of sulphate of lime we must make a = 10, and 

 then three-sevenths of the quantity required for steam must be let out, and one-fourteenth of the 

 effect of the fuel will be lost. It may be necessary to explain, that sulphate of lime does not appear 

 to exist in sea water till a change of combination among its constituents takes place through eva- 

 poration ; also, it requires thirty-six parts of salt to saturate one hundred of water at 226, but it 

 appears that deposit takes place at 228 with only thirty parts. 



3 The best method would be to use a cock to let out the water from the condenser, placed so low 

 as to completely drain it, and the water should be let out in the first instance ; then the steam 

 should be let on, and as soon as steam issues at the cock, it should be closed, till it be evident that 

 the cylinder is as hot as the steam will render it ; then open the cock again till steam has passed 

 out a few seconds, and close it, confining the steam to the top of the piston, and open the injection, 

 when motion will commence if the operation has been properly performed. 



