368 Mr. G. F. Emery. [Apr. : 



salts. A few trials with alcohol in the D-tube were made, but w 

 not very successful, owing to the rapid effects of diffusion in tin- 

 beaker constantly altering the E.M.F. at constant temperature. 



Lastly, I endeavoured to prove by experiment that these then 

 electric forces at the junctions of metals and solutions are part o 

 system of reversible thermodynamic phenomena. For this to be ti 

 we require to prove the equation 



3 = dEjdt = H/f, 



where H is the heat developed by the passage of unit of electric 

 across the junction, t is the absolute temperature of the junction, a 

 is the quantity discussed above. 



As far as I am aware, M. Bouty alone has attempted this previou 

 (' Journ. de Phys.,' vol. 9). He used the plated bulbs of two sinx 

 thermometers as electrodes, noticing the difference between tl 

 readings when the current was allowed to pass in different directio 

 He graduated them in terms of heat units by sending a curn 

 through a spiral coil of fine wire enclosing one of the bulbs. 1 

 values of H which he so obtained compare fairly well with those 

 t(dEjdf) measured directly. This method seems to depend rather 

 much on the steadiness of convection currents in a liquid to be qu 

 reliable, and I "have tried several arrangements to avoid this difficu 

 with, I think, satisfactory results. 



Some very good observations were obtained with an apparatus 

 the ordinary calorimeter principle. It was made up of the follow: 

 parts, fig. 6 : 



A. The Measuring Apparatus. This consists of a double bobbin 

 thin sheet copper on a hollow core, on the lower end of which 

 screwed a metal plate (), which forms the electrode, and is in cl 

 proximity all over its inner surface with the lower side of the bobl 

 The lower half of the bobbin (/3) is wound with very fine copper wi 

 the resistance of which forms the thermometer. The upper half 

 the bobbin (7) is wound with platinoid wire, having a resistance 

 9*58 ohms. This platinoid coil formed the heater, by means of wh 

 a known quantity of heat could be put into the calorimeter, and 

 this way its heat capacity could be measured. 



B is a revolving stirrer which passes through the core of A, a 

 rests on a thin metal plate. 



The calorimeter vessel, C, is a thin glass tube, drawn out at 

 lower extremity, through which passes the stem of the lower electro 

 D, which is a circular plate of metal ; over D are porous plates, 

 protected from the stirrer by a thin sheet of metal. 



All the vessel above this sheet of metal is enclosed in a metal lj 

 F, and all above D is in a wooden box, G, which is surrounded 

 all sides by fossil meal. 



