VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 519 



which might escape a more regular astronomer. But whoever can, ought to do 

 more. By degrees the exact positions of every star he has noted down may be 

 ascertained, by the method practised by Mr. de la Caille in his Southern Hemis- 

 phere, or by any other which shall be esteemed more convenient. To render this 

 more complete, it were to be wished that each should give in a copy of his origi- 

 nal observations, with an account of the instruments he used ; since they ought 

 to be preserved as data whence his deductions were made, which may then be re- 

 examined at any future time. Yet must it be desired that no one would trust 

 himself without carrying on his calculations as fast as the observations are made : 

 they will otherwise multiply on his hands till the labour will dishearten him from 

 attempting it at all. A heap of crude, undigested observations would be an un- 

 welcome present to the public. 



Since my former papers, the longitude of this place (Chislehurst) has been 

 ascertained by comparative observations on the bursting of some rockets, let ofF 

 on purpose; which, on a mean of several, turns out to be 1Q S .02 in time e. of 

 Greenwich Observatory; that is, it may hereafter be considered as 19 s , instead of 

 19 s . 6 as I had before calculated it trigonometrically from the bearings. 



Mr. W. then adds a collection of new astronomical observations, made since 

 his last communication ; the first of which is an eclipse of the moon, <$ July 30, 

 i770 ■ observed with a 34- feet achromatic telescope, and a power magnifying 29 

 times (that is, a single eye-glass belonging to the day-tube) the aperture of the 

 telescope being reduced to 1^- inches. The night very clear and still. The be- 

 ginning was not properly observed : the several spots on the moon's disc were 

 there noted when eclipsed. At 1 l h 7 m 57 s , apparent time, the eclipse was seemingly 

 total. The beginning of the emersion judged to be about ]2 h 43 m s . The end 

 of the eclipse was at ] 3 h 42 m s . 



2. The next is an observation of an eclipse of the sun, $s June 24, 1778: 

 observed with a 3^ feet achromatic telescope magnifying 75 times. The aperture 

 reduced to 2 inches, to prevent breaking the smoked glasses. The beginning at 

 3 h 40 m 334- s ap. time ; and the end at 5 h 25 m 24 s . 



3. The 3d is an eclipse of the moon <$ November 23, 1779 : observed with 

 the same telescope, magnifying 75 times. The aperture reduced to 2 inches. 

 Night clear and frosty. No wind. The eclipse total at 7 h 7 m 31 s ; the moon's 

 edge began to emerge at 8 h 46 m 23 s . The end could not be seen for the haze. 



4. The 4th is an eclipse of the sun, $ Oct. 16, 1781: observed with the same 

 telescope and magnifying power. The beginning not visible ; sun too low. The 

 end at 20 h 22 m 13 s .5. 



5. The 5th was an eclipse of the moon, $ Sept. 10, 1783 : observed with the 

 same telescope, viz. 34- feet achromatic, with the aperture reduced to 2 inches ; 

 but with a small magnifying power of 36 times, made by Mr. Dollond. The 



