28 On the Solar Eclipse 



It by no means appeared so great as the diminution which 

 took' place in November 1816: ahhough in that eclipse only 

 •78 of the sun's disc was obscured, whereas in the present one 

 •87 was obscured. But the former eclipse I observed through 

 the dark atmosphere of London, where the abstraction of a 

 small portion of light is easily perceptible. And I understand 

 that, in the present eclipse, the diminution of light during the 

 middle of the eclipse was very perceptible in the metropolis, 

 and at places where the sun was obscured by clouds. Venus 

 was seen by thousands of spectators with the naked eye: and 

 I am informed that Mars also was visible to many. 



Mr. DoUond mformed me that he took the horizontal dia- 

 meters of the sun and moon, at Greenwich, with one of his 

 divided object-glass micrometers ; and that they were in the 

 proportion of 3-351 to 3' 103, Therefore, assuming the semi- 

 diameter of the sun, as deduced frem Delambre's tables, as 

 a standard, the apparent semidiameter of the moon will be 

 14' ^^''jH; being about one second less than my own obser- 

 vation. The times at which Mr. Dollond and Mr. Taylor 

 observed the conunencement and end of the eclipse, at the 

 Royal Observatory, were as follow: 



DoIXOND. 



Beginning = Q^ 22' 37" 

 End =3 14 40 



Duration 



Taylor 

 0" 22' 33",6 

 3 14 

 2 52 



2' 33",6 -^ 



4 44,5l "^^'^^t"^\^'^^ 



2ll079J Greenwich. 



= 2 52 3 



Mr. Groombridge has favoured me with the following ob- 

 servations of the eclipse at Blackheath: N. lat. 51° 28' 2", 

 E. long. 0",67 in time from Greenwich. End of the eclipse 

 at S^ 14' 34" mean time at the place: the beginning not ac- 

 curately observed. 



Vertical distance of the Cusps. 



Each revoliuiou of the micrometer was equal to 44",982. 



The 



