various British Standards of linear Measure. 339 
TABLE IV. 
Further Comparisons of the Distance from Zero to Forty Inches 
of General Roy’s Scale, with the Forty-inch Bar. 
Difference be- Roy’s scale 
Readings. | tween the scale/Correction for | shorter than 
and the bar in |Temperature. | the 40-inch 
Roy. | inches, bar. 
30 — 000043, —°001740 *001783 
26 + ‘000086 — 001823 ‘001737 
30 — 000000 —°001906 *001906 
5 + “000300 — 002104 *001804 
89 + °000171 — 001856 “001685 
13 — 000556 — 001276 
14 — 000514 — ‘001276 
14 — 000599 —°001276 
15 — 000577 —'001276 
16 — 000556 —°001326 
Mean 
Adding to the mean thus obtained -00C034, the excess of 
one sixth of Ramsden’s bar above the forty-inch bar, we have 
*001849 of an inch for 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 comparisons con- 
tained in Table I. only 000117 of an inch, a difference 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 II]. by comparing each standard in succession, with 
that used by Colonel Lambton in the survey of India. 
Excess of the following standards above Colonel 
sMek 
Lambton’s standard. On 36 inches. 
Sir G. Shuckburgh’s standard, sd eoeee.| +°000642 
Bird’s standard of 1760 ...........6--] -+°000659 
General Roy’s scale ........+-00¢5--04] | +°001537 
Royal Society’s staudard .......-08+-+-) -+°002007 
Ramsden’s bar (used in the Trigonome- . 
trical Survey of Great Britain) ...... | #008147 
If the results of the two series of comparisons made by Dr. 
Wollaston be examined, it will be seen that the greatest difference 
from those above given, is not two ten-thousandths of an inch, 
and this difference appears to have arisen almost wholly from the 
ill defined dots of the Royal Society’s standard. 
The standard used ia the Trigonometrical Survey, being thus 
unexpectedly found to differ so considerably from every other 
etandard of authority, the Commissioners of Weights and Mea- 
Uu2 sures 
