1884.] Energy and Radiation in Incandescence Lamps. 163 



fitted at the other side of the pile. C is a tube to be connected with, a 

 pump for exhausting the chamber in which the couples are placed, 

 the ends of which are the glass or other plates. There is outside 

 this chamber another hollow chamber through which a current of 

 water can be passed, the intake being by B, which is connected by an 

 india-rubber tube P to the water supply. F is an ordinary pinchcock. 

 G is a screw of 30 turns to the inch by which the pile can be moved 

 along the guides QQ. The base is let into a wooden block which is 

 screwed down to the observing table. It will be seen that the height 



FIG. 3. 



of the pile can be adjusted. TT, one not shown in the figure, are the 

 terminals which are connected, with the pile and the galvanometer. 

 The face of this thermopile was placed in the spectrum and moved 

 along it, the deflections of the galvanometer being noted at the 

 different parts for the different currents passed through the lamp. 

 The slits were adjusted so as to be approximately equal to one 

 another, and were kept of an aperture of about -fa inch. The 

 galvanometer used was one of very low resistance, and set up so as 

 to be exceedingly sensitive. The currents and potentials were 

 measured by Thomson's graded galvanometers, but in some cases the 



M 2 



