2Q'2 OBSERVATIONS OF THE ECLIPSE 



5 June 11 tli, astronomical time, with the reflector, power 

 100, observed an immersion of Jupiter's 1st satellite at 1 l h 18' 

 16i." per clock: clouds were passing, and a thin vapour over- 

 spread the disk of Jupiter; it is conjectured that the true time 

 of the immersion might have been 10 or 15 seconds later. 



June 12th. Equal altitudes of the sun's lower limb. 



A. M. Double altitude P. M. 



t ' a o h / it 



At 9 8 47 102 at 2 50 52 4 Index on 18' 22" 



11 7 i 103 48 32 off 44 46 



By these the clock was fast for mean time 31" 58, and by 

 a comparison with those of the 5th and 9th, the clock loses at 

 the rate of 0" 368 per day, which correction being applied to 

 the time per clock, of the immersion of Jupiter's 1st satellite, 

 we shall have for the moment of the immersion, 11" 17' 44" 644 

 mean time. The longitude deduced from this observation 

 would be 6" 5' 41" 4, or 91° c 25' 21" West of Greenwich. 



June 15th, astronomical time. Prepared to observe the 

 eclipse of the sun, which (from calculation) was expected to 

 begin soon after 20 h ; at 19 1 ' got the telescopes prepared: found 

 a great undulation upon the limb of the sun, seen through the 

 six-feet reflector; the red colour of the image was offensive to 

 the eye; I therefore gave the preference to the line mild yellow 

 image (most perfectly defined) of a 1\ feet achromatic tele- 

 scope, belonging to a set of astronomical circles, although the 

 power did not exceed 40. 



The moment of the expected impression approached, and 

 reflecting that this eclipse was to be seen all over Europe and 

 North America, which renders it a very important phenomenon 

 for settling comparative longitudes, I conceived that all the 

 zealous astronomers of both worlds were then looking with me 

 at the great luminary and centre of our system : I kept my eye 

 riveted upon that point of the disk where the eclipse was to 

 commence, with an anxiety known only to astronomers; with 

 the chronometer watch at my ear, I attended to the most doubt- 

 ful appearances which my perturbation perhaps presented to the 

 eye, and upon every alarm, began to count the beats of the 

 watch, (five in two seconds) in order that 1 might not lose the 

 very hist instant of the impression, and I am confident that not 

 4D!ie" quarter of a second was lost, of the time when the impre?- 



