520 



Mr EL Tomlinson. The Influence of 



of "Young's modulus " by the method of static extension was tested 

 with nearly the same loads, both temporary and permanent, as in the 

 last experiment, with the following results : — 



Permanent 

 load in kilos. 



Temporary 

 load in kilos. 



Temporary alteration 

 of length in 

 half-millimetres. 



Temporary 

 alteration of 

 length per kilo. 



i 



2 



£ 



2-70 



5-40 



i 

 2 



1 



5-49 



5-49 



1 



n 



8-29 



5 53 



i 

 2 



2 



11-41 



5-76 



H 



i 



2 



2-37 



4-74 



2i 



1 

 2 



2-37 



4-74 



1 



1 



2-54 



5-08 



The numbers given in the third column are the means of several 

 trials and, with the exception of the last two, require a slight correc- 

 tion, inasmuch as it was evidently impossible with such a small per- 

 manent load as % kilo, to obtain a sufficiently straight wire,* The 

 correction, however, can be easily applied, for we see that when the 

 permanent load is equal to 1-| kilos, a temporary load of -| kilo, 

 produces precisely the same temporary elongation as when the per- 

 manent load is 2 \ kilos., or, in other words, kilos, must have 

 sufficed to make the wire straight. Thus with a permanent load 

 of kilo, the apparent increase of length caused by the mere 

 straightening of the wire is 2*70 — 2*37, or 0*43 when ^ kilo, is the 

 temporary load, and will be 0'43 + 2 , 53 — 2'37, or 0*59 when the tem- 

 porary load is either 1 kilo, or greater than 1 kilo. Making the above 

 corrections, and placing side by side the alteration of length and the 

 alteration of resistance produced by each additional \ kilo., we obtain 

 as follows : — 



Number 

 of | kilos. 



Temporary alteration 

 of resistance for each 

 successive £ kilo. 



Temporary alteration 

 of length for each 

 successive i kilo. 



1 



4-4 



237 



2 



6-4 



2-63 



3 



8-7 



2-80 



4 



11-9 



3-12 



We may notice that though, in consequence of imperfect elasticity, "t 

 * A matter of no importance in the electrical experiments. 



t The recovery of length was as complete as the recovery of resistance had been 

 on the removal of the stress, and this is no doubt due to the cause previously 

 mentioned. 



