128 Observations on the Annular Solar Eclipse, 



are well known, I have found the longitude of the place, by my 

 observations of the beginning of the eclipse, to be IS"" 22s.26 W. 

 and by the end 12"' 41 ^6 W. The first of these deviates about 

 20« from the truth, the second 2' only, and the mean of 

 both about 11% arising from the errors in the solar and lunar 

 tables combined with the errors of observation. When the ob- 

 servations made at the Royal Observatory of Greenwich, and 

 other places whose longitude is well determined, are obtained, 

 a comparison of these will fix the longitude of my station with 

 greater certainty ; though from the results above it is clear that 

 in distant countries, where corresponding observations cannot 

 be often got, the longitude may in this manner be found, by 

 repeated observations, to a very great degree of accuracy. In 

 observing eclipses, the complete phase is generally that most 

 attended to, because the precise time of peculiar intermediate 

 states is not easily attained. I had originally proposed to 

 mark the time when the ring was partially formed, and only 

 broken occasionally by the lunar mountains, but I found some 

 uncertainty ift determining that state of the eclipse. By sweep- 

 ing the eye along the serrated limb of the moon, I could not 

 determine precisely the mean level of the moon's surface, or the 

 circular line equidistant from the centre, and I was therefore 

 doubtful whether the parts of the limb of the sun broken by. 

 dark intervening spots, were entirely mountains or not ; and the 

 short space of time allowed for consideration did not permit me 

 to come at any conclusion by reason and reflection. The esti- 

 mated time in some cases, from the light first breaking through 

 what might be readily taken for valleys at the point of nearest 

 contact, till the luminous arch reached the summits of the moun- 

 tains, at both the formation and termination of the ring, taken, 

 of course, in inverse order, was about five seconds, more or less, 

 in my judgment, according to circumstances; but I have not 

 recorded these among what I conceive to be decidedly good ob- 

 servations. I marked the time of entrance of some of the spots 

 too, but as these observations also must be very vague, I have 

 not communicated them. 



These broken particles of light, already alluded to, intersect- 

 ed by the serrated peaks of the lunar mountains, produced a 

 very interesting and brilliant effect, and had a good deal of the 

 appearance of elongated particles of mercury arranged in a nar- 



