Astronomical Society. 229 



IV. Extract of a letter from Mr. Henderson to Mr. Baily, rela- 

 tive to the late Annular Eclipse of the Sun on May 15, 1836. 



After correcting the places of the sun and moon, and their semi- 

 diameters, by the quantities mentioned in my last letter, I computed 

 the beginning and end of the eclipse, and of the annulus ; and 

 I annex the computed times of these phsenomena, and also the ob- 

 served. 



Computed Observed 



sid. Time. Time, 



h m s h m s 



Beginning of eclipse 5 6 9-2 not observed . 



At formation of annulus. 



First appearance of detached luminous portions of 



sun's limb 6 30 4M 



Internal contact of sun and moon 6 30 ■16"2 



Annulus completely formed by disappearance of 



blacii spots G 30 50-1 



At dissolution of annulus, 



Annulus broken by appearance of black spots 6 31 33-0 



Internal contact of sun and moon 6 34 40'3 



Disappearance of detached luminous portions of 

 sun's limb G 34 44-0 



EudofecHpse 7 53 7-5 7 53 ^ig | 



It thus appears that the true internal contacts happened between 

 the moments when the beads of light were obser^'ed to appear and 

 disappear, and when the black spots disappeared and appeared. At 

 the formation of the annulus, when the beads appeared, V'-Q of the 

 moon (a segment of that maximum breadth) seems to have been be- 

 yond the sun's disc ; and when the black spots disappeared, the an- 

 nulus was 1"-1 in breadth, where least. This agrees with the ap- 

 pearance observed, " that the annulus was seen completely formed 

 of sensible breadth at the narrowest part." Again, at the dissolu- 

 tion of the annulus, when the black spots appeared, it is found that 

 the least breadth of the ring was 2"-3, also agreeing with the actual 

 observation, that " the annulus, being of sensible breadth, was sud- 

 denly broken ;" and when the beads disappeared, l"-2 of the moon 

 was beyond the sun's disc. The same telescope was used for ob- 

 serving the formation and dissolution of the annulus, and for makino- 

 the observations from which the corrections of the elements have 

 been determined. 



On applying the same corrections, I find that in latitude 55° 27' 30'' 

 N. and longitude 10'" 12^0 W. of Greenwich, the true internal con- 

 tacts were at 



Observed by you at 



Mean time, 

 h. m. s. 



3 :u 

 3 .'•> 23 



Duration =0 4 34 



Duration = 4 20 



I suispect that the longitude of your station is not well determined; 

 but. as a small error in the longitude will not sensibly affect the du- 



