404 Mr. H. Tomlinson on the Increase in Resistance 





Number of pounds 

 employed to stretch the 

 wire. 



Increase per pound, 

 reckoned in divisions of the 

 sliding scale. 



Steel (No. 1). 



Section in square inches 

 determined from loss of 

 weight of a given length 

 of the wire in water at 

 4°C = 2231x10-7 



Total length of wire em- 

 ployed =27-46 feet. 



2 

 3 

 4 



5-75 



8- 42 



9- 75 

 12 

 12-5 



36-8 

 36-8 

 36-9 

 36-8 



36- 8 



37- 

 36-7 

 36-4 



Mean.. 36-78 



Steel (No. 2). 



Section in square inches, 

 6528x10-7. 



Total length of wire em- 

 ployed = 27-5 feet. 



2-75 



8 

 16 

 20 

 24 

 28 



12-72 

 12-52 

 12-52 

 12-52 

 12-52 

 12-32 



Mean.. 12-52 



Steel (No. 3). 



Section in square inches, 

 12563x10-7. 



Total length of wire em- 

 ployed =27-65 feet. 



8 

 12 

 14 

 20 

 28 

 40 



6-07 



6-07 

 6-05 

 6-06 

 6-08 







Mean. . 6-069 



Though a smaller number of different weights were employed with the 

 other wires, the proportion of the increase of resistance to the stretch- 

 ing-weight was quite as exact as in the case of the three examples given, 

 never less than three different weights being used, and each of these 

 tried several times. 



The increase of resistance which a cubic centimetre of each wire would 

 experience when stretched by a weight of 1 gramme was then calcu- 

 lated, and also the resistance of a cubic centimetre of each wire in ohms 

 determined. The former values will be denoted by h, and the latter by 

 the letter 5. 



The following Table gives the values of h, s, the section of each wire 

 in square inches, and its specific gravity : — 



