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
"At the door from the Front Court to the staircase of the Octagon Room
(the original entrance to the Observatory as erected by Sir
Christopher Wren), a small porch-shelter has been often desired. I
proposed to fix there a fan-roof of quadrantal form, covering the
upper flat stone of the external steps.--On a critical examination of
the micrometer-screws of the Transit Circle it was found that the
corrections, which range from -1°38" to +0°76", indicate considerable
wear in the screws; and it was found that as much as one-hundreth part
of an inch had been worn away from some of the threads. The old screws
were consequently discarded, and new ones were made by Mr Simms.--The
adjustment of the Spectroscope has occupied a great deal of
attention. There was astigmatism of the prisms; and false light
reflected from the base of the prisms, causing loss both of light and
of definition. The latter defect was corrected by altering the angles,
and then astigmatism was corrected by a cylindrical lens near the
slit. The definition in both planes was then found to be perfect.--The
number of small planets has now become so great, and the interest of
establishing the elements of all their orbits so small,--while at the
same time the light of all those lately discovered is very faint, and
the difficulty and doubt of observation greatly increased,--that I
have begun to think seriously of limiting future observations to a
small number of these objects.--All observations with the Spectroscope
have been completely reduced; the measures of lines in the spectra of
elements being converted into corresponding wave-lengths, and the
observations of displacement of lines in the spectra of stars being
reduced so as to exhibit the concluded motion in miles per second,
after applying a correction for the earth's motion. Sixteen measures
of the F line in the spectrum of the Moon as compared with hydrogen
give a displacement corresponding to a motion of less than two miles a
second, which seems to shew that the method of comparison now adopted
is free from systematic error; and this is supported by the manner in
which motions of approach and recession are distributed among the
stars examined on each night of observation. The results recently
obtained appear to be on the whole as consistent as can be expected in
such delicate observations, and they support in a remarkable manner
the conclusions of Dr Huggins, with regard to the motions of those
stars which he examined.--Photographs of the sun have been taken with
the photoheliograph on 182 days. On one of the photographs, which was
accidentally exposed while the drop slit was being drawn up, there
appears to be a faint image of a cloud-like prominence close to the
sun's limb, though the exposure probably only amounted to a fraction
of a second. A prominence of unusual brilliancy was seen with the
Spectroscope about the same time and in the same position with
reference to the Sun's limb. All groups of Sun-spots and faculae have
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