On April the 26th, 1722, Bradley read
his inaugural lecture in that new position on which he was destined
to confer such lustre.
It must, of course, be remembered that in those early days the art of
constructing the astronomical telescope was very imperfectly
understood. The only known method for getting over the peculiar
difficulties presented in the construction of the refracting
telescope, was to have it of the most portentous length. In fact,
Bradley made several of his observations with an instrument of two
hundred and twelve feet focus. In such a case, no tube could be
used, and the object glass was merely fixed at the top of a high
pole. Notwithstanding the inconvenience and awkwardness of such an
instrument, Bradley by its means succeeded in making many careful
measurements. He observed, for example, the transit of Mercury over
the sun's disc, on October 9th, 1723; he also observed the dimensions
of the planet Venus, while a comet which Halley discovered on October
the 9th, 1723, was assiduously observed at Wanstead up to the middle
of the ensuing month. The first of Bradley's remarkable
contributions to the "Philosophical Transactions" relates to this
comet, and the extraordinary amount of work that he went through in
connection therewith may be seen from an examination of his book of
Calculations which is still extant.
Pages:
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215