14 PROCEEDINGS OF THE AMERICAN ACADEMY 



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 2^- 48'"- 31'- side- 

 real 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 ob- 

 servations 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 exist- 

 ence 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 fre- 

 quently 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 ; — 



h. ni. s. 



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, B' denotes W. C. Bond. 



B2 " Geo. P. Bond. 

 W " Captain Wilkes, U. S. N. 

 P " Professor Peirce. 



