various British standards of linear measure . 8 7 
By the above comparisons. General Roy's scale appears to 
be shorter than the 40 inch bar ,001698 ; to which adding 
,000034, the quantity by which Ramsden’s bar exceeds the 
40 inch bar, we have ,001732 of an inch for the difference 
in defect between General Roy’s scale and the standard used 
in the Trigonometrical Survey, with which it was supposed 
to be identical. 
TABLE II. 
Comparisons of the distance from zero to 40 inches of Sir George 
Shuckburgh's scale with the 40 inch bar. 
Date. 
Temp. 
Readings. 
Difference between 
the scale and the 
bar in inches. 
Correction 
for 
Temperature. 
Shuckburgh’s scale 
shorter than the 
forty inch bar. 
Bar. 
Shuck. 
May 7 
59,° 
2 3 
75 > 2 
—,002234 
— ,000829 
,003063 
9 
65,0 
4M 
62 
— ,000877 
— ,001 823 
,002700 
65,2 
4 * 
58 
— ,000778 
—,001856 
,002584 
6 5 > 3 
30 
49 
-—,000813 
— ,001873 
,002686 
65.3 
3 ° 
5i 
— ,000899 
—,001873 
,002772 
64,7 
27 
5° 
— ,000984 
— ,001773 
,002757 
10 
67,4 
36,2 
4 M 
— ,000227 
— ,002220 
,002447 
67,8 
33 
44 
— ,00047 1 
— ,002287 
,002758 
12 
6 7 > 5 
42 
48 
— ,000257 - 
— ,002237 
,002494 
Mean 
,002696 
If to the above mean ,000034 be added as before, we have 
,00273 an inch , by which the distance from zero to 40 
inches of Sir George Shuckburgh’s scale is shorter than one 
sixth part of Ramsden’s bar. 
The very great difference between Ramsden’s bar and 
General Roy's scale, made me desirous of comparing this 
last with the Royal Society's standard, and as I was aware 
of the existence of other standards of considerable importance, 
I resolved to examine them at the same time. 
The Royal Society's scale has been described by Sir George 
