Autobiography of Sir George Biddell AiryAiry, George Biddell
Science
Autobiography of Sir George Biddell Airy
Airy, George Biddell
Airy, George Biddell, 1801-1892; Astronomers -- Great Britain -- Biography; Autobiographies; Royal Greenwich Observatory
"In the Report to the Visitors, when on the subject of the Altazimuth,
the following paragraph occurs: 'I alluded in a preceding section to
the cutting away of a very small portion of one of the rays of the
three-armed pier which carries the Altazimuth. The quality of the
brickwork is the best that I have ever seen, and not a single brick
was disturbed beyond those actually removed. Yet the effect was to
give the Altazimuth an inclination of about 23". This inclination
evidently depends on the elasticity of the brickwork.'--With reference
to the new S.E. Equatoreal the Report states that 'The support of the
north or upper end of the polar axis has been received, and is planted
within the walls of the building in a position convenient for raising
it to its ultimate destination. It is one piece of cast-iron, and
weighs nearly 5 tons.'--Small changes as previously mentioned had been
noticed with regard to the Zero of Azimuth of the Transit Circle, and
the Report states that 'In regard to the Azimuth of the Transit
Circle, and the Azimuth of its Collimator, Mr Main has brought
together the results of several years, and the following law appears
to hold. There is a well-marked annual periodical change in the
position of the Transit Circle, the southerly movement of the eastern
pivot having its minimum value in September, and its maximum in March,
the extreme range being about 14 seconds; and there is a similar
change, but of smaller amount, in the position of the Collimator. I
cannot conjecture any cause for these changes, except in the motion of
the ground. There is also a well-marked connection between the state
of level of the axis and the temperature. The eastern pivot always
rises when the temperature rises, the extreme range being about 6
seconds. I cannot offer any explanation of this.'--Under the head of
Extraneous Works the Report states that 'The British Government had
for some years past contributed by pecuniary grants to the preparation
of Prof. Hansen's Lunar Tables. In the last winter they undertook the
entire expense of printing a large impression of the Tables. The
reading of the proof-sheets (a very considerable labour) has been
effected entirely at the Observatory. I may take this opportunity of
stating that the use of these Tables has enabled me, as I think,
incontestably to fix the capture of Larissa to the date B.C. 557, May
19. This identification promises to prove valuable, not merely for its
chronological utility, but also for its accurate determination of an
astronomical epoch, the point eclipsed being exactly known, and the
shadow having been very small.'--In April I gave a lecture to the
Royal Astronomical Society on the methods available through the next
25 years for the determination of the Sun's parallax.--Dr
Livingstone's observations for African longitudes were computed at the
Observatory.--The Admiralty enquire of me about the feasibility of
adopting Piazzi Smyth's construction for steadying telescopes on board
Public-domain text, read in full here on John Shaqi.
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