J. 0. Thompson — Law of Elastic Lengthening. 43 



p- 



x observed. 



x calculated. 



Observed-calc. 



kg- 



mm. 



mm. 



mm. 



0-2 



5-531 



•529 



+ 0-002 



0-4 



11-084 



•086 



- 2 



0-6 



16-671 



•673 



- 2 



0-8 



22-298 



•294 



+ 4 



1-0 



27-949 



•951 



__ 2 



1-2 



33-646 



•646 



=fc o 



Mean temperature, 13° -5 

 Cross-section of wire, 0*0641 mm. 2 

 Length of wire, 22690 mm. 

 Specific gravity of wire, 8*99 

 Initial load 0-192 kg. 



The figures of the third column were calculated according 

 to the equation 



x— 27-578 p + 0-3193 p 2 + 0-0538 p\ 



The initial load was 0*192 kg. Measurements showed that 

 0-15 kg. sufficed to hold the wire straight, while O'lO kg. was 

 insufficient. 



Experiments with Steel Wire. 

 The following table gives the mean result of 20 series of 



p- 



x observed. 



x calculated. 



Observed-calc. 



kg. 



mm. 



mm. 



mm. 



0-2 



7*078 



•077 



+ o-ooi 



0'4 



14-196 



•197 



— 1 



0-6 



21-358 



•358 



± 



0-8 



28-558 



•558 



=h 



1-0 



35-792 



•793 



— 1 



Mean temperature, 13° 

 Cross-section of wire, 0-03263 mm. a 

 Length of wire, 22700 mm. 

 Specific gravity of wire, 7'74 

 Initial load, 0-491 kg. 



The figures in the third column were calculated according 

 to the equation 



x= 35-2725 p-\- 0-5725 p 2 -0'0525 p 3 



An evidence of the insignificance of the after-effect may be 

 seen in the fact that in ten successive series of measurements 

 the lengthening caused by the maximum load deviated in no 

 case more than -0225 mm. from the mean. Two minutes after 

 the release of the wire the mean position of the zero- point was 

 •01 mm. lower than immediately before this maximum load 

 was put on the pan. 



