various British standards of linear measure. 91 
TABLE IV. 
Farther comparisons of the distance from zero to forty inches of 
General Roy's scale , with the forty inch bar. 
Date. 
Temp. 
Readings. 
Difference between 
the scale and the 
bar in inches. 
Correction 
for 
Temperatnre. 
Roy’s scale shor- 
ter than the forty 
inch bar. 
Bar. 
Roy. 
Tune iq 
64,5 
29 
3 ° 
— ,000043 
— ,001740 
,001783 
65,0 
28 
26 
+ ,000086 
— ,001823 
,001737 
6 5-5 
30 
3 ° 
— .OOOOOO 
— ,001906 
,001906 
66,7 
12 
5 
+ ,000300 
— ,002104 
,001804 
65,2 
93 
89 
+ ,000171 
— ,001856 
,001685 
20 
61,7 
0 
13 
— ,000556 
— ,001276 
,001832 
— 
2 
14 
— ,0005 14 
— ,OOl 276 
,001790 
— 
0 
H 
— ,000599 
— ,001276 
,001875 
— 
5 
15 
— ,000577 
— ,001276 
,001853 
— 
3 
16 
— ,000556 
— ,001326 
,001882 
Mean 
,001815 
Adding to the mean thus obtained ,000034, the excess of one 
sixth of Ramsden's bar above the forty inch bar, we have 
,001849 °f an inch f° r the excess of 40 inches of the standard 
used in the Trigonometrical Survey, above General Roy's 
scale, differing from the result given by the former compa- 
risons contained in Table I. only ,000117 of an inch, a differ- 
ence which may be attributed to uncertainty of temperature. 
The mean of both ,00179, is probably very near the truth. 
I shall now proceed to give in one view, the results deduced 
from Table III, by comparing each standard in succession, 
with that used by Colonel Lambton in the survey of India. 
Excess of the following standards above Colonel 
On 36 inches. 
Lambton’s standard. 
Sir G. Shuckburgh’s standard ... 
+,000642 
Bird’s standard of 1760, .... 
+ ,000659 
General Roy’s scale .... - 
+ ,001537 
Royal Society’s standard ... 
+ ,002007 
Ramsden’s bar (used in the Trigonometrical Sur-^ 
vey of Great Britain) . - . / 
t 
+ ,003147 
