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gation, and for observations of the moon.
Whenever a meridian transit of the moon
could be observed this was done. But, even
so, there are periods in the month when
the moon is too near the sun for a tran-
sit to be well observed. Also weather in-
terferes with many meridian observations.
To render the lunar observations more con-
tinuous, Airy employed Troughton’s succes-
372