45, CORNHILL, B.C., AND 122, REGENT STREET, W., LONDON. 485 







FIG. 2958. 



2958 Ferguson's Pyrometer, in its most complete form, fitted up with an Oil or 



Water Batli for uniformly heating the metal rods under experiment, the 

 Temperature of the Bath being shown by a delicate Thermometer fitted to 

 it ... Price, complete with Bath and Thermometer (fig. 2958) 



5 10 



2959 Wedgewood's Pyrometer: with this instrument the degree of heat is 



estimated by the permanent contraction of a prepared Cylinder of Pipe- 

 Clay or Porcelain; but its indications (except for one or two special 

 purposes) are found to be fallacious and of little practical value. Supplied 



to order. 







For Gauntletfs, Bystroin's, and Siemen's Pyrometers, see pages 203 and 204. 



2960 Fire Syringe, for exhibiting the evolution of Heat by 



the rapid Compression of Air. This is the converse 



of Leslie's experiment (page 475), in which Cold is 



produced by the rapid rarefaction of air . . .056 086 

 29t>l Metal Bar and Gauge, for showing, in a simple and 



conclusive manner, the expansion of metals by heat 



(fig. 2961) 076 



The Metal Bar when at the ordinary temperature of the air will fit tightly 

 into the gauge ; but if it be warmed, the metal will be expanded, and prevent the 

 bar from fitting into the gauge until it is again cooled. 



2962 Gravesand's Metal Ball and Ring, for exhibiting the 



same fact , 10 6 



2963 Compound Metal Bar, to exhibit in a striking manner the Expansion and 



Contraction of metals by heating and cooling. This bar is made of two 

 slips of metal of differing expansibility by heat (Iron and Brass). When 

 Cold this bar is perfectly straight, but if heated by the flame of a Spirit 

 Lamp it becomes curved . Price, for Bar only 60 086 



2964 Compound Metal Bar, with Stand, large size, for Lecture 



Table 15 



2965 Compound Metallic Bar Thermometer, (Brequet's), in 



the form of a Watch 440 



See also the Metallic Clinical Thermometers, Medical Section, for an adaptation 

 of Breguet's Instrument. 



