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The instrument used in these observations was a 46-inch Transit, made by Troughton and Simms ; 21-inch object-glass.

2. TRANSIT OF MERCURY, MAY 8Th, 1845.

“ The first and second contacts of the planet with the sun's limb were lost by clouds.

“Mercury was first seen on the disk of the sun at 2h. 48m. 31" sidereal time. Observations for the relative positions of the planet and the sun were immediately commenced, and were continued throughout the transit, though frequently interrupted by the passage of cumulus clouds, which prevailed through the day.

“The tremulous state of the atmosphere towards the close of the observations was unfavorable to the accuracy of the measurements.

“ It was thought, at one time, that a luminous spot was visible near the centre of the disk of the planet ; any decisive evidence of its existence was precluded by the limited power of the instrument.

" At the last contact, the singular phenomenon of the inosculation of the adjacent edges of the planet and sun was distinctly noticed by both observers. The present instance is one of much interest, as it has hitherto been supposed that Mercury is not thus affected when in close proximity to the sun's limb, although this sort of phenomenon has frequently been noticed in the transits of Venus (see Mem. Royal Ast. Soc., Vol. X.).

“The third and fourth contacts were pretty well observed, but owing to the oblique and slow motion of the planet across the sun, combined with the unsettled state of the atmosphere, we were unable to note the times of contact with sufficient accuracy to be of much value for the purposes of terrestrial longitude. The times noted were as follows:

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Third contact,

9 09 00 Observer, W. C. Bond.
9 08 58

Geo. P. Bond.
Last or fourth contact, 9 12 09 " W. C. Bond.

9 12 00

Geo. P. Bond.

“In the following observations, Bi denotes W. C. Bond.

B2 1 Geo. P. Bond.

Captain Wilkes, U.S.N. P " Professor Peirce.

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