THE KEW NATIONAH STANDAED OF LENGTH, AND ITS PEINCIPAL COPIES. 648 
The Ordnance Bar lA was now put in the place of the Koyal Astronomical Society’s 
scale, and lA and 2 A were both supported on rollers. 2 A is longer than lA, — 
o inch. 
1844, Jan. 17, from 20 comparisons at temperature 38‘25, by 0’000423 
18, from 20 comparisons at temperature 41 ‘6 5, by 367 
20, from 20 comparisons at temperature 42'55, by 311 
22, from 20 comparisons at temperature 44T0, by 359 
23, from 20 comparisons at temperature 43T2, by 313 
Three bars (the Eoyal Astronomical Society’s scale, lA and 2A) were now mounted 
together ; the Eoyal Astronomical Society’s scale being furthest from the observer, and 
2A nearest to him. lA and 2A were supported each on its own semicircular pieces, 
which were carried by the same supporting bar. The Ordnance Bar lA is longer than 
the Eoyal Astronomical Society’s scale, — 
o inch. 
1844, March 13, from 10 comparisons at temperature 42'67, by 0-002203 
14, from 10 comparisons at temperature 42-13, by 2520 
15, from 10 comparisons at temperature 43-82, by 2140 
And Ordnance Bar 2A is longer than the Eoyal Astronomical Society’s scale, — 
„ inch. 
1844, March 13, from 10 comparisons at temperature 42-67, by 0-001875 
14, from 10 comparisons at temperature 42-13, by 2055 
15', from 10 comparisons at temperature 43-82, by 1751 
Here lA appears longer than 2A ; whereas the previous observations had made 2A 
longer than lA. The only circumstance with which this discordance could be con- 
nected was this : that when (as in this instance) the two iron bars were supported by 
brass semicircular pieces resting upon the same T-bar, it was necessary to place cards 
under the brass semicircles of lA, in order to bring them to the same height. 
- The Ordnance Bars lA and 2A were now mounted, each on its own semicircular 
pieces, and on separate T-bars. The Bar 2A is longer than lA, — 
1844, March 16, from 20 comparisons at temperature 46°-25, by 0-000211 inch. 
The arrangement was then altered, merely by placing cards under the semicircular 
pieces of lA and depressing its T-bar properly. The Bar lA is then longer than 2A, — 
1844, March 18, from 10 comparisons at temperature 44°-0, by 0-000054 inch. 
Then the semicircular pieces (those of lA having cards beneath them) were placed on 
the same T-bar. The Bar 2A is longer than lA, — 
1844, March 19, from 10 comparisons at temperature 45°-0, by 0-000318 inch. 
1 shall depart from chronological order, for the purpose of inserting two series of 
