182 Mr. Baily on an [Sept. 



efforts will avail, I have drawn up the following memoir, under 

 the hope that it may induce others, who have more leisure, and 

 are at the same time more conversant with the subject than my- 

 self, to pursue the inquiry, and suggest further hints to those who 

 may have an opportunity of observing this rare phenomenon. 



M. de L'Isle, in his Avertissement above alluded to respecting 

 the eclipse of 1748, suggested the advantage and propriety of 

 some scientific person in the principal states of Europe through 

 which the shadow of the moon's umbra passed undertaking to 

 announce to the inhabitants the several observations which it 

 would be proper for them to make ; and afterwards to collect 

 and arrange such observations for further investigation, if suffi- 

 ciently convinced of their accuracy. A similar plan might be 

 adopted in the present instance ; and, from the more general 

 diffusion of science, would be more likely to be attended with a 

 beneficial effect. Such collections of observations (when made) 

 should be sent by the different collectors to one or more of the 

 principal astronomers of Europe, in order that they might be 

 finally investigated, and the result laid before the public. 



With that view I would take this opportunity of requesting 

 those into whose hands the present memoir may fall to circulate 

 it as much as possible on the continent, and amongst those 

 persons who, from their connexion with any foreign literary 

 journal, may be likely to diffuse the subject of it amongst the 

 inhabitants of that part of Europe and Africa where the annular 

 appearance will be observed. Such of our own countrymen, 

 likewise, that may be travelling in any of the provinces on the 

 continent here alluded to, will promote the interest of astronomy 

 if they would carefully note down or collect any of the circum- 

 stances hereinafter alluded to, or indeed any other remarkable 

 phenomena that may happen during this eclipse. I shall be 

 happy to receive any observations of this kind that may be 

 forwarded to me, and will preserve the result of them, as above 

 proposed, for a future investigation. 



The elements of the present eclipse I have computed from 

 M. Burckhardt's tables of the moon, and M. Delambre's tables 

 of the sun ; and they are as follow. The ecliptic conjunction 

 will take place on Sept. 7, 1820, at 



l h 51' 37" 3 p. m. apparent time, orl . n • i 



1 49 26 2p.m.^«»t 1 me....../ atGreemvlch: 



And at that time we shall have the 



True longitude of the luminaries 5 s 14° 47' 40-7" 



True latitude of the moon (north) 00 44 39-4 



Moon's horary motion from the sun 00 27 1-7 



horary motion in latitude (decreasing) 00 2 42*0 



horizontal parallax 00 53 53-0 



— — semidiameter 00 14 41-0 



