102 



Mr R. A die on Electrical Experiments. 



primary current in its passage along CAB. I made the following 

 experiments. 



Two bars of bismuth and antimony, 8 inches long each, were tied 

 together in the form of letter V, and ribbons of copper fixed to 

 their upper ends for connecting with a battery, — the joint of the 

 bars was placed in the bottom of a conical wine-glass, beside a 

 delicate thermometer, and a small quantity of water, sufficient to cover 

 the thermometer bulb and the joint. The heating power of a hydro 

 current, derived from a single pair used in experiments (37), was 

 now tested by observing the change of temperature of the water. 

 The duration of each trial was 30', and an interval of 30' intervened 

 betwixt every experiment, to allow the temperature of the parts to 

 settle. Then the antimony was replaced b^ a similar bar of copper, 

 and another set of results taken. Again lead was substituted for 

 the copper, and the heating effects similarly tested. The observed 

 results were — 



rent, passing from the thermo positive Battery current, passing from the 

 r^ thfi tliprmn nPirntJvA r«ofpi thermo negative to the thermo 



Battery cm ,^ o --- - 



to the thermo negative metal. 



Bismuth and antimony couple gave 3° increase 

 in temperature. 



copper 2 



" ■ Oi 



ppe 

 id.. 



positive metal. 



Gave 9° increase in tempera- 

 ture. 



5 



2 



The bars used in the foregoing experiments were now tied up in the 

 form fig. 2 ; the bismuth bar being connected with each of the other 

 3 in the same order as above. A feeble current of electricity derived 

 from a pair of plates excited by water only, was then passed through 

 BAG, and the action on the galvanometer attached to F and G noted. 

 The deflections were not very regular in their extent ; to compensate 

 for this, I took the mean of a number of experiments, omitting the 

 fractional parts as unnecessary, bismuth and antimony gave 48" 



copper ... 16 



lead ... 8 



Here the action on the galvanometer corresponds with the changes 

 of temperature produced by similar joints immersed in water, from 

 which I infer, that the currents in M. Pelletier's cross are the results 

 of differences of temperature only ; and, in a variety of experiments, 

 made with thermo joints, I have never seen any evidence of a re- 

 duction of temperature or cold. The arrangement which produced 

 the widest difference in temperature of a joint heated by a current, 

 passing, first, in one direction, then in another, was, when the bismuth 

 and antimony couple, used to heat water in a wine-glass, were ar- 

 ranged with a piece of the bar of bismuth projecting beyond the joint 

 into the water, which did not touch the bar of antimony. The cur- 

 rent passing from the thermo positive metal increased the tempera- 

 ture 2°, the contrary current 12"^. 



39. The experiments I have now submitted, appear to me to offer 



