Page:Philosophical Transactions - Volume 054.pdf/347

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.

[ 281 ]

the planet presently became distinct, and her limb well defined. Upon this, I applyed myself to observe the passage of the Sun's and Venus's preceding limbs, by the vertical, and of their lower limbs by the horizontal, wires in the reflector, and made the following observations; one of my assistants counting the clock, and the other writing down the observations as I made them; which, having made the proper correction of the time for the change of the Sun's declination, stand as follows.

True time. diff. long. & Lat. South.
h , ,, , ,, , ,,
At 4 21 20 Sun at the vertical 10 47
31 Venus at the same 9 2
23 6 Venus at the horizontal 9 4 10 50
24 23 Sun at the same
27 29 Venus at the horizontal 9 25 10 52
28 47 Sun at the same
35 15 Sun at the vertical 10 55
21 Venus at the same 9 56
37 49 Venus at the horizontal 10 8 11 00
39 9 Sun at the same

As Venus began now to draw near the Sun's limb, I prepared to observe her egress. The interior contact did not appear so perfectly instantaneous, as Dr. Halley's papers led me to expect. I was not certain of it till 4h 47′ 21″, though I doubted of it at 17″. The exterior contact I judged to be at 5h 5′ 49″, doubtful also 3 or 4″; and so the passage of Venus's diameter, 18′ 28″.

The above observations gave me several altitudes and azimuths of Venus, from whence I deduced her

Vol. LIV.
O o
right