91 
RESEARCHES 
UNDERTAKEN AT THE REQUEST OF THE ASSOCIATION. 
Report on the Comparative Measurement of the Aberdeen 
Standard Scale. By Francis Baily, Treas. Royal So¬ 
ciety , fyc. 
Agreeably to the request of the British Association I 
have compared the Aberdeen standard scale with the standard 
scale of the Royal Astronomical Society: but, as in a matter 
of this nicety and importance I did not wish the results to 
depend on my own comparisons only. I obtained the assistance 
of Mr. Bryan Donkin, Lieut. M. Johnson, Mr. Thomas Jones, 
and Mr. William Simms, all conversant with and much versed 
in micrometrical measurements, and who kindly lent me every 
assistance in their power. 
The centre yard of the Aberdeen scale was chosen as the ob¬ 
ject of comparison with the centre yard of the Royal Astrono¬ 
mical Society’s scale; that being the portion of the latter scale 
which had been directly compared with the Imperial standard 
yard prior to its loss by fire, at the destruction of the two 
houses of Parliament in November last. The following are the 
results of 56 comparisons made by the several parties above 
mentioned, and estimated in divisions of the micrometer mi¬ 
croscopes (each division denoting ^oboo an i nc h>) and show 
the number of such divisions by which the centre yard of the 
Royal Astronomical Society’s standard scale exceeds the centre 
yard of the Aberdeen scale. 
1835. 
No. of 
Comp. 
Divisions of 
Micr. 
Temp. 
Observers. 
Feb. 16. 
8 
26-56 
4°8-6 
Baily. 
— 18. 
8 
27-74 
46-4 
Donkin. 
- - 
16 
29-16 
48-9 
Donkin and Johnson. 1 
— 19. 
8 
27-09 
45-8 
Jones. 
— 20. 
8 
27-65 
45-3 
Simms. 
— — 
8 
26-93 
46-2 
Baily. 
Mean = 
j 
56 
27-71 
46-9 
. 
