188 NEGRETTI AND ZAMBEA, HOLBOEN VIADUCT. E.G., 



FIG. 515. . FIG. 515*. 



Each Each 



s. d s. d. 



508 Volumeter (Gay Lussac's), for liquids lighter or heavier 



than water 066 



509 Densimetre (Gay Lussac's), for liquids lighter or heavier 



than water, in two spindles simple form ... 086 



510 Ditto (Rousseau), for ditto ditto ditto . 086 



511 Photographic Hydrometer, or Argentometer, showing 



grains per ounce of nitrate of silver in solution . 036 



512 Hydrometer Test Glasses, or Jars, on foot 



(figs. 512 and 515*) 2s. 3 6 056 



513 Salinometer Glass, for ascertaining the density of salt 



water in steam-boilers, to prevent incrustation (fig 471.) 056 



514 Ditto ditto, Gilt Metal, in tin case (fig. 466) 18 



515 Ditto Ditto, Gilt Metal or German Silver in Box, fig. 467 1 1 



516 Ditto with Thermometer in Mahogany box ... 1 12 



517 Salinometer Thermometer (fig. 469) . 066 



518 Ditto, Testing Pot, Stout Copper, with division for 



Thermometer. 086 



The Salinometer used for testing the density of water in Marine Steam Boilers 

 has a scale with five principal divisions marked upon it, the first division on the 

 top of the stem is marked 0, representing pure water, the others marked 3 ' 2 | 2 3 $ 

 and 3 4 5 signify that when the Salinometer floats at any of these divisions, that the 

 water contains 1, 2, 3, or 4 parts of saline or solid matter in 32 of water. 



Between 5 2 5 and 3 3 5 is engraved the word Blow, indicating that when the Boiler 

 Water has reached that density, a portion of it should be blown out of the boiler 

 and replaced with fresh water. The temperature at which the water is to be tested 

 is 200 Fahr. 



At the 3 2 5 the word " Limit " is marked, when, at that indication, it becomes 

 dangerous to work it beyond that strength or density. 



Thus, this Instrument purports to indicate the precise time at which Marine 

 Steam Boilers should be blown off, not only to prevent waste by blowing off too 

 frequently, but to avoid the possibility of the Boiler being injured by the deposition 

 or incrustation of the salt, which is a bad conductor of heat, and frequently the 

 cause of the Boiler being burst. The engineer, by merely looking ab the scale of 

 the Salinometer as it floats in the water, can at once ascertain the saline density 

 of the water with the greatest accuracy. 



