INTRODUCTION. xlvii 
METEOROLOGICAL INSTRUMENTS. 
§ 8. BAROMETER. 
55. A Mountain Barometer, by ADIE & Son, was used from July 1841 till 
January 1842. The scale is engraved on the brass tube, and reads, with a vernier, 
to 0.002 in.; the mercury in the limb of the cistern is adjusted at each observation 
to a constant zero point ; the tube is about 0.15 inch diameter. 
56. After January 1. 1842, a Standard Barometer, by Newman, was placed in 
the Observatory. The diameter of the boiled tube is 0,552 in. ; the scale is attached 
to a brass rod, terminating in an ivory point, which, at each observation, is made to 
meet its image in the mercury of the cistern. The vernier professes to read to 
0-002 in., and 0-001 may be estimated ; but the graduation is so inexact, as to give 
changes in error from 0-002 to 0-003 in. 
The barometer by NEWMAN was compared indirectly with the standard of the 
Royal Society, London, by means of one belonging to the DuKE of ARGYLE. The 
comparisons were made in London. 
TABLE 23.—Comparisons of the Duke of Argyle’s Standard Barometer with the Standard 
Barometer of the Royal Society of London. 
Royal Society’s Standard. Duke of Argyle’s Standard. i 
rror 
of Duke of 
T 1 Corrected to Tem- | Argyle’s 
Flint Glass. Crown Glass. semper: Height. empera- | perature of R. 8. || Standard. 
wares vanes Standard. 
in. in. he in. ® in. in. 
29-280 29-274 36-9 29-302 37-2 29-301 + 0-024 
29-490 29-482 39-0 29-496 39-0 29-496 +0-010 
29-462 29-454 40-0 29-460 40:6 29-458 + 0-000 
29-252 29-246 41-6 29-256 42-0 29-255 + 0-006 
29-366 29-358 41-3 29-372 42-0 29-370 +0-008 
29-210 29-204 43-2 29-214 43-5 29-213 +0-006 
The mean correction of the Duke of Argyle’s Barometer to the Royal Society’s 
is — 0.009. 
