ON STANDARDS FOK USE IN ELECTRICAL MEASUREMENTS. 



135 



Either of these two methods seems to give satisfactory results. For 

 completely annealing silver wires the temperature of the paraffin bath 

 is not sufficiently high, but from the results of my measurements for 

 silver, for which the influence of annealing is very considerable, it can be 

 seen that the first method is quite satisfactory. 



Silver. 



Many of the older measurements for resistances and conductivities are 

 expressed in terms of the resistance of pure silver : this was the case with 

 Matthiessen's earlier results. 



Some measurements therefore made on silver wires are given, together 

 with the results obtained by Matthiessen and Profs. Dewar and Fleming 

 for the sake of comparison. 



Several samples of silver wires were supplied by Messrs. Johnson and 

 Matthey : one of tliese was stated to be absolutely pure. 



The results are expressed for wires weighing one gramme per metre. 



The difference between the values for the hard-drawn wires is probably 

 due to the fact that they had to be further drawn down after I had 

 received them to enable me to measure them on my bridge. 



Profs. Dewar ^ and Fleming give as the value for an annealed pure 

 silver wire 1468 C.G.S. at 0° C. with the temperature coefficient of 'OOJ: j 

 the value at 18° is therefore for the specific resistance 1574. 



For most of the wires which I measured the specific gravities were 

 determined ; for the wires Silver I. there is practically no difference between 

 the values obtained for the annealed and hard-drawn wires, the values 

 varying from 10'496 to lO'Sll. 



For the wires Silver III. the values varied from 10"49 to 1050 ; 

 using the mean value 10"495 I get for the specific resistances the following 

 values : — 



' Using the value 10"5 as the specific gravity of silver. 

 - Phil. Mag., vol. xxxvi. 



