0.05 

 0.05 

 0.05 

 0.05 i^ 

 05 5 



0.05 4.3 



On thescale,' 

 or after o 1 



Inch. 



0.05 

 0.05 

 0.05 

 0.05 

 O.Oj 



0.05 

 0.05 



0.00 



Ver. 



11 

 11 



12 



l^ 



15 



12.3 

 4.3 



8.0 



Mean on the scale. 

 Mean off the scale. 



Difference. 



VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 46l 



without the micrometer, and then putting it on, and measuring the distance at 

 which obiects are seen distinctly, he assumed 



•' 1 / // Off the scale, ' 



the sun's apogeal diameter to be 31 28", as or before o. 

 given by Mr. Short; and, on that hypothesis, inch.,vI7 

 the reductions of the parts of the micrometer 

 are made. Its error was determined immedi- 

 ately before the beginning of the eclipse, by mea- 

 suring the angle subtended by a small ball 

 which is on the top of the spire of St. Bride's 

 church, in Fleet-street, alternately before and 

 after O, or the beginning of the divisions of the 

 scale: these measurements were as annexed : 



Half the above difference, or 4 divisions of the vernier, = 4".83, is the error 

 of the micrometer, to be subtracted from the measured distances of the cusps, 

 and also from the diameters of the sun, taken near the middle of the eclipse, 

 in the same direction with the chords which were measured about the same time: 

 and, this direction being nearly vertical, these measurements will, in some 

 degree, be affected by refraction; but they may readily be corrected if the alti- 

 tudes of the sun be computed to the times when they were taken, and thence 

 the effect of the refractions. 



The beginning of this eclipse was at S*" SQ"^ 47% apparent time, very exact; 

 and the end at 5^ 25™ 14■^ The same mean diameter, at the time of the 

 eclipse, was 3l' 27".8. 



XLVI. An Eclipse of the Sun, June 24, 1778, observed at Leicester. By the 

 Rev, Mr. Ludlam, Vicar of Norton, near Leicester, p. 10 IQ. 



The beginning was observed at S'^ 35'" 27'; the end at 5^ JQ*" 30» or 34^ 

 according to the time shown by the clock, the sun being a little hazy at the end 

 of the eclipse. But the clock being 1™ 22' faster than the sun, the beginning 

 will be 3^ 24"^ 5% and the end at 5^ 18™ 8' or 12% solar time. 



The difference between the meridians of Greenwich and Leicester, from 

 observations in the Philos. Trans., computed by Mr. Wales, as below: 



From solar eclipse June 3, 1769 } g^f °"^S 4- 2V5 



^ Tauri, April 28, 1770 Immersion 4 27. 8 



Aldebaran, Nov. 18, 1774 Emersion 4 50. 5 



4 23.2 



4 41.3 



Solar eclipse, June 24, 1778 } £^|'""'"S 



M. du Sejours, in the Memoirs of the Academy of Sciences for J 771, makes 

 the difference of the meridians of Paris and Leicester, from the end of the 

 solar eclipse of 1769, to be 13™ 39'; and the difference of the meridians of 



