of the Coefficient of Expansion of Pure Nickel. 
which is calculated so as to agree with the experimental 
eurve at 100°, 200°, 300°. Above 300° this formula does 
a, =10-*(1280 + °75¢ + °0035¢7)* 
not agree with experiment. 
From 380° upwards the coefficient is constant, and has the 
value ‘0000191. 
Of the two tables which follow, the one is an example of the 
values of the expansion actually observed, and shows how the 
observations were reduced, while the other gives values of the 
mean coefficient of linear expansion. 
| 

| Distance | / 
between | Shift of | Shift of | Value of | 
Scratches at) Left-hand |Right-hand) 0. | .o45¢ ONi 
beginning | Scratch. | Scratch. ie St 
| of range. | 
| 1032000 © 01565 02345 | -00780 1445 
10°32780 | 01016 01655 ‘U0639 | 1654 
10°33419 ‘01890 02820 00930 2114 
1034349 | -03825 06110 | -02285 3165 
10°36634 | -02423 03495 =| -01072 “3894 
1037706 | ‘01976 02920 =| -00%44 "4144 
10°38650 | -02068 ‘02935 | 00867 |  -4360 
1039517 | -04094 | -06160 | 02066 | -4760 

10°41583 RGM ic) aa tie ee 
Mean Values of the Coefficient of Expansion. 
| 
| 
| 

Range of 
633 
It can be represented up to 300° by the parabolic formula 




Mean 


Temperature range. 
Lower. 
16°4 
15:5 
pi 
182°3 
305:0 
364-2 
3950 
442:°0 
539-0 

Upper. 
| | 
. 
*).* 
e). 
_ 
= . 
‘ 6 
& . 
=). 
Fe 




Temperature. Temperature. or 
0 to 50 25°0 ‘0000128 
50 ,, 100 750 ‘0000136 
150 ,, 200 175°0 ‘0000151 
250 ,, 300 2750 / ‘G000174 
300 ,, 350 325°0 ‘0000191 
300 ,, 565 3979 ‘0000205 
380 ,, 400 390-0 | ‘0000191 
400 ,, 450 425°0 : ‘0000189 
450 ,, 500 4750 | 0000192 
500 ,, 550s 525-0 | ‘0000190 
* Cp. Tutton’s value for nickel 
at=10-8 (1248+ -‘74f) 
(Proc. Roy. Soc. Nos. 415-419). 
