TRANSACTIONS OF SECTION A. 



641 



Papers,' art. Iv. In that article it is stated ' that a feeble continued current, 

 passing out of an electrolytic cell by a zinc electrode, must generate exactly as 

 much more heat at the zinc surface than the same amount of current would 

 ■develop in passing out of an electrolytic cell by a platinum electrode, as a zinc 

 platinum pair working against great external resistance would develop in the 

 resistance wire by the same amount of current.' 



In the first set of experiments two equal and similar glass vessels were used 

 with about 500 c.c. of dilute sulphuric acid in each. The pairs of elements were 

 Zn, Zn ; Zn, Pt. The rise of temperature, due to currents of from 4 to 14 milli- 

 ■amperes, obtained from the Smee cell, was observed at intervals of a few minutes 

 for about four hours. There are many sources of errors in this mode of experi- 

 menting, but generally the rise of temperature of the Zn, Zn cell was greater 

 than that in the Smee cell. In some of the experiments the Smee cell showed a 

 higher rise of temperature ; but this latter result is no doubt due to local causes, 

 such as polarisation, &c. 



In the second set of experiments a current of 39 milliamperes was obtained 

 from the Smee cell, and in every case the rise of temperature of the Zn, Zn cell 

 was greater than the rise of temperature of the Smee cell, and the average rise 

 corroborates the statement of Lord Kelvin quoted above. 



In the third set of experiments the two elements in each cell were separated 

 by a piece of blotting-paper, and four thermometers used to indicate the rise of 

 temperature at each electrode. It was found that the rise of temperature at the 

 iinc anode plate was greater than at the zinc cathode. 



In another series of experiments with four cells containing dilute sulphuric 

 ■acid in which the pairs of elements were Zn Zn, Pt Pt, Pt Zn, Zn Pt, currents 

 from an external source of ^, 1, and 2 amperes, were allowed to flow for about an 

 hour, and the rise of temperature in each cell recorded. Tables of results are 

 given showing that the rise of temperature in the cell in which the current flowed 

 from platinum to zinc is in every case higher than the rise of temperature in the 

 •cell in which the current flows from zinc to platinum. Taking the average of a 

 number of experiments fairly agreeing among themselves, it is found that the 

 mean rise of temperature in the four cells above the rise of temperature of the 

 laboratory is — 



<- Direction of Gurrent. 



Mr. George E. Allan, Thomson Scholar in the Physical Laboratory of the 

 University of Glasgow, has carried out the greater number of the later 

 experiments. 



2. On the Electric Conductivity of Bismuth and Copper in Magnetic Fields. 



By Dr. W. Peddie, F.R.S.il. 



2. The Application of Interference Methods to Spectroscopic Measurement. 

 By Professor A. MiCHELSON.^See Reports, p. 170. 



4. Photographs of Electrical Discharges. 

 By A. A. Campbell Swinton. 



The photographs exhibited were all obtained without the employment of anv 

 lens, and were produced by merely causing the electric discharges to take place 



1892. T T 



