THE NEW NATIONAL STANDAED OF LENGTH, AND ITS PEINCIPAL COPIES. 645 
Mr. Bailt then made the following comparisons of measures defined by lines cut on 
different parts of the Koyal Astronomical Society’s Tube. Near to the two extremities 
of the 5-foot tube, transversal lines had been cut (known by the letters A, a) crossing 
the continuation of the line of the divided scale ; then, supposing the tube to be turned 
round its axis through 90°, two similar transversal lines B, b, were cut ; turning the tube 
90° further, two similar lines C, c, were cut, which therefore were on the side of the 
tube opposite to A, a ; turning the tube 90° further, two similar lines D, d, were cut. 
The comparison of the longitudinal intervals between these was the object of the follow- 
ing observations : — 
1844, April 21, at temperature 60°, by six comparisons in each case, the excesses of 
the various measures above Aa were as follows : — 
inch. 
B5 exceeds Aa by — O'OOOOOO 
Cc exceeds Aa by -j- 0-000126 
exceeds Aa by — 0-000015 
In 1835 the corresponding differences were 
-0-000056 
-1-0-000056 
-0-000169 
This was the last special inquiry on which Mr. Baily was engaged. 
Mr. Baily died on 1844, August 30. 
The state of the problem at this time, as regarded the restoration of the Standard, 
was nearly as follows. The object might be considered : either to reproduce in a satis- 
factory form the value of the Scientific Standard (Shuckbuegh’s), which Captain Katek 
considered as a scientific representative of the National Standard of Length ; or to repro- 
duce the Legal Standard. With regard to Shuckbuegh’s scale: the experiments of 
Mr. Baily had confirmed the remarks which originated with Captain Katee himself, that 
minute circumstances, whose effect was totally unsuspected in the earlier comparisons of 
this scale, produced a disturbance in the apparent length, which might have deranged 
in different directions the results of its comparisons for physical measures, and whose 
magnitude was intolerably great ; that there was no security whatever that, in retaining 
documentary or numerical expressions of measure founded on this scale, we were referring 
to a consistent system ; and that in future it would be better to lay aside this scale 
entirely. With regard to the Legal Standard : the principal difficulty, inherent in the 
standard itself, arose from the size and irregular form of its defining dots, which indeed 
made accurate comparison impossible. With regard to the existing scales which had 
been compared with the Legal Standard : the Tubular Scale of the Royal Astronomical 
Society (complicated in its mechanical structure) was found to have changed, in itself, 
and by comparison with similar scales, in a way and to an amount which ruined its 
credit ; the Ordnance Bars (of firm and simple structure) appeared in themselves trust- 
MDCCCLVII. 4 p 
