45, CORNHILL, E.G., AND 122, EEGENT STREET, W., LONDON. 



PYROMETERS. 



594 Gauntlett's Pyrometer. This Pyro- 

 meter is constructed of metal bars expanding 

 in a different ratio upon the application of 

 heat, by which can be ascertained tempera- 

 tures above the range of the mercurial ther- 

 mometer. Its form is that of a long tube, 

 surmounted by a dial with an index or pointer 

 to indicate to 300 for fluids, or to 1,009 for 

 furnaces, ovens, &c. (fig. 594) .... 



595 Chronometrical Pyrometer Thermo- 

 meter (Gauntlett's), with 8-day time-piece to 

 indicate to 300 or 1,009 . 



596 Daniell's Pyrometer, for indicating high 

 temperatures, such as the melting point of 

 metals, temperature of furnaces, &c., by the 

 expansion of a bar of Platinum enclosed in a 

 black lead cylinder, and measured by an index 

 arranged with a spring and lever, to show 

 upon a divided arc very small changes . 



597 Wedgwood's ditto, for the same 

 purpose, by the expansion of a Cylinder of 

 earthenware ...... 



Each 

 3 d. 



440 



8 10 



550 



550 



598 Ferguson's ditto, for showing the differ- 

 ence of expansion in metals, suited for the 

 lecture table as an experimental instrument .550 



599 Hydro Pyrometer, Captain O. Bystrom's (Swedish 

 Artillery), for ascertaining the heat of furnaces, &c. 

 A ball of platinum, or other metal, is arranged upon a 

 metal rod in such a manner that it can be inserted into 

 the furnace to be tested, and when heated equal to the 



FIG. 594. temperature of the furnace quickly withdrawn and 

 dropped into a given quantity of water. By observing the temperature of the water 

 before and after the above-mentioned procedure, the difference obtained will be th^ 

 value or amount of heat of the furnace 1 15 



This Pyrometer is the most simple and practically useful of any of the above at 

 very high temperatures. Price for Thermometer, Copper Bolt and Wooden 

 Water Vessel. 



Further details respecting Pyrometers will be given in our section on" 

 Chemical Apparatus. 



