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The reflection of the micrometer wires and
of a star very near the zenith (but not quite
in the zenith) can be observed together. His
mercury trough was a circular plane surface
with a shallow edge to retain the mercury.
The surface quickly came to rest after dis-
turbance by street traffic.
Sir W. M. H. Christie, Eighth Astronomer
Royal, took up his duties in that capacity
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