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ing these variations; and in the year 1907
as many as 1,545 observations of stars were
made with the reflex zenith tube.
In connection with zenith telescopes it
must be stated that Respighi, at the Capi-
tol Observatory at Rome, made use of a
deep well with a level mercury surface at the
bottom and a telescope at the top pointing
downwards, which the writer saw in 1871.
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