OF ARTS AND SCIENCES. 307 



lo = 



See the curve representing the resistance in this exjieriment. There 

 is a great and rapid change in the resistance vvlien the wire has been 

 stretched 20 centimetres. 



n L81_ _ „ ^ R _ 4776 



lo' ~ 2.055 — -'"^ To — 6"2r6 "'^^ 



,.. R I' 

 Here at this point -p- < tt. 



Experiment 4. — In tliis experiment I used thicker copper wire, 

 with the following results : — 



I 



I tried the same kind of wire again. It stretclied considerably 

 before there was any change in the resistance. The original length 

 was 1.65 metres. The final length was 1.82 metres. 23 lbs. broke the 

 wire before I had time to ob.serve the resistance; but, before api)lying 

 the last pound, the resistance was .076 ohms. Tlie original resi.stance 

 was .072. 



/2 2.622 R R ^ P 



l{' 3.312 •' A'l A\ -^ /j^ 



Experiment 4b was with the same kind of wire, with these re- 

 sults : — 



