282 Mr Russell on a Marine Salinometer for indicating the 



In like manner fresh water and salt water (fig. 3) will stand 

 at heights of 40 and 41 inches, shewing a difference of 1 inch. 



The use which I make of this principle is as follows : — I 

 reckon the best scale of saltness of a boiler to be that which 

 takes the common sea-water as a standard. Sea-water con- 

 tains 5^0 of saline matter. When the water has been evapo- 

 rated, so as to leave only half the qviantity of distilled water 

 to the same quantity of saline matter, I call that two degrees 

 of salt, or brine of the strength of two, and such brine would 

 shew, in fig. 3, the columns 40 and 42, or double the saltness of 

 sea-water, indicated by a difference of 2 inches. A farther 

 saturation would be indicated by a difference of 3, 4, 5, and 

 6 inches between the columns, and so indicate three, four, five, 

 six, and any further degrees of saltness — a range which may 

 be made to any degree of minuteness by the subdivision of the 

 scale of inches. This scale is that which appears to me most 

 simply applicable here — and it is that which I adopt for marine 

 boilers. 



The mechanical apparatus which I have employed to give 

 this indication is perfectly simple, and has the advantage of 

 being such as the engineer already perfectly understands. To 

 the marine boiler I apply two water-gauges of glass, instead of 

 one as at present used ; they both serve the purpose of the 

 present glass gauges, and the pair would be valuable for this, 

 if for no other reason, that there would always be a duplicate 

 when one is broken, an accident not unfrequent. To these 

 gauges I simply attach small copper pipes, so that one of them 

 may be placed in communication only with the salt brine in 

 the lower part of the boiler, and the other with the feed-water 

 which is entering the boiler ; the one then holds a column of 

 brine, and the other of pure sea-water, and each inch of dif- 

 ference shews the degree of saturation. 



Without the use of any attached scale, the engineer, by a 

 little practice, comes to know in his particular vessel what dif- 

 ference in inches can be admitted without danger, and at what 

 difference of height it is imperative to blow off. But it is con- 

 venient to have an attached scale. 



It may be satisfactory to state, that the practical range of 

 scale in an ordinary boiler in the ordinary working, is 6 to 10 

 inches, a difference sufficiently great to be easily observed. 



