86 
Captain Kater on the comparison of 
It may be seen in the former part of this paper, that the tem- 
perature at which the points were laid off on Mr. Ramsden’s 
bar from the brass scale, was 54,°; consequently, the observed 
lengths of the brass scales and 40 inch bar, must be re- 
duced to this temperature. The expansion of one foot of 
General Roy’s scale for one degree of the thermometer was 
found by him to be ,0001237, and of one foot of Ramsden’s 
bar ,0000740 of an inch ; consequently, the excess of the 
expansion of 40 inches of the scale, above 40 inches of the 
bar, for each degree above 54 0 will be ,0001657 of an inch ; 
and this quantity has been used in computing the corrections 
for temperature. 
The comparison of both scales with the bar was made at 
the same time; but to avoid confusion, I have given the re- 
sults in separate tables. The scales and the 40 inch bar were 
laid together two days previously to commencing the ex- 
amination. 
TABLE I. 
1 , 
Comparisons of the distance from zero to 40 inches of General 
Roy’s scale with the 40 inch bar. 
Date. 
Temp. 
Readings. 
Difference between 
the scale and the 
bar in inches 
Correction for 
Temperature. 
Roy’s scale short- 
er than the forty 
inch bar. 
Bar. 
Roy. 
May 7 
59 >° 
2 3 
3 2 »5 
■—,000407 
—,000829 
,001236 
8 
62,0 
14 
23 
— ,000385 
— ,001326 
,00171 1 
9 
65, 0 
4*>5 
43*5 
— ,000086 
— ,001823 
,001909 
65,2 
4 1 
40 
+ ,000043 
— ,001856 
,001813 
6 5’3 
3 ° 
26 
+ ,000171 
—,001873 
,001701 
6 5>3 
3 ° 
29 
+ ,000043 
— ,001873 
,001829 
64,7 
27 
2 S 
+ ,000086 
— ,001773 
,001687 
xo 
67,4 
36,2 
24 
+ ,000522 
,002220 
,001698 
Mean 
,001698 
