204 



NEGBETTI AND ZAMBRA, HOLBOEN VIADUCT, E.G., 



SIEMENS' WATER PYROMETER. 



JFiyl, 



600 The PYROMETER is shown in figs. 1 and 2 in 

 margin (fig. 1 being a vertical, and fig. 2 a horizontal 

 section), and consists of a copper vessel capable of 

 holding rather more than a pint of water, and well 

 protected against radiation by having its sides and 

 bottom composed of a double casing, the inner com- 

 partment of which is filled with felt. A mercury 

 thermometer, b, is fixed in it, having, in addition to 

 the ordinary scale, a small sliding scale c, graduated 

 and figured with 50 degrees to 1 degree of the 

 thermometer scale ; 6 solid copper cylinders are 

 provided with the Pyrometer, each accurately 

 adjusted in size, so that its total capacity for absorb- 

 ing heat should be l-50th that of a pint of water. 



In using the Pyrometer, a pint (0*568 litre, or 

 34'66 cubic inches) of water is measured into the 

 copper vessel, and the sliding pyrometer scale c is 

 set with its zero at the temperature of the water as 

 indicated by the mercury thermometer b ; a Copper 

 Cylinder d is then put into the furnace or hot blast 

 current the temperature of which it is wished to 

 ascertain, and is allowed to become heated for a time 

 varying from 2 to 10 minutes according to the 

 intensity of the heat to be measured. 



It is then to be withdrawn and quickly dropped 

 into the water in the copper vessel, where it raises 

 the temperature of the water in the proportion of 

 1 for each 50 of the temperature of the copper. The 

 rise of the temperature may then be read off at once 

 on the pyrometer scale, and if to this is added the 

 temperature of the water as indicated on the mercury 

 thermometer before the experiment, the exact tem- 

 perature required is obtained. 



For very high temperatures Platinum cylinders 

 may be employed instead of Copper. 



Price of Siemens' Water Pyrometer, with Thermometer and six copper 

 cylinders, complete 440 



Water Pyrometer, with Thermometer and six wrought-iron cylinders, 

 complete . . . . , . .400 



