3 J 4 



UNIVERSITY OF COLORADO STUDIES 



reach the higher temperature owing to the liberation of atomic energy. 

 Any considerable difference in heat development ought to be capable 

 of detection by suitably placed thermoelectric couples and a sensitive 

 galvanometer. It was on this basis of theory that the experiments were 

 undertaken. 



The experimental difficulties were unusually great and necessitated 

 many preliminary experiments to overcome 

 them. The arrangement of apparatus finally 

 adopted is shown in the figure which is an axial 

 section. The vacuum tube was about 20 cm. 

 in length by 3 cm. internal diameter. The 

 kathode was a flat piece of aluminum of about 

 2 cm. diameter insuring a bundle of rays con- 

 siderably larger than the target offered by the 

 plates. The anode A was a brass cap forming 

 a Faraday cylinder. On opposite sides of this 

 brass cap were cut two windows (not shown 

 in the figure) covered by glass and wire gauze, 

 which permitted an inspection of the positions 

 of the plates and thermoelectric couples at all 

 times. The Zn plate was 1 . 1 cm. long, 3 cm. 

 wide and 0.075 cm - thick; the Pb plate 1.1 

 cm. long, 3 cm. wide and 0.025 cm - thick. 

 The difference in thickness was to allow for 

 the difference in conductivity. Both the con- 

 ductivity and the specific heat of zinc are ap- 

 proximately three times that of lead. Both 

 plates rested upon a vulcanite ring sunk flush 

 with the surface of the brass plate, as indicated 

 in the figure. The openings beneath the plates 

 were of exactly the same size, 1 cm. by 0.2 cm., and symmetrically 

 placed in the bundle of kathode rays. To prevent static charges affecting 

 the galvanometer, the plates, the brass cap, and the galvanometer case 

 were earthed. The wires by which the plates were earthed were exceed- 

 ingly fine and of the same length, so that what little loss of heat occurred 



