Solar Eclipse. 305 



if a conjecture may be hazarded, the cause is, perhaps, to be 

 looked for in some property of the sun itself*. 



At the termination of the eclipse, although a small trian- 

 gular portion of the moon's periphery could be seen, when 

 every other part had passed off the solar disc, not the least 

 appearance of refraction, or any indication of an atmosphere 

 could be perceived. For some moments after egress, the moon 

 totally disappeared, but the observation was anxiously con- 

 tinued, in hopes of realizing M'De Isle's suggestion. About 

 2" from the sun's margin, the finely attenuated film of pale 

 light was descried, which gradually increasing, at length ap- 

 peared to extend along nearly ^ of the moon's circumference, 

 exhibiting at the same time considerable breadth, much greater, 

 indeed, than could have been supposed considering its extreme 

 proximity to the sun. The colour of the illuminated surface 

 was similar to, but more faint than, that of the moon, when 

 sometimes seen during the day. The light towards the extreme 

 points seemed to disappear by degrees ; at the centre it shewed 

 more acutely defined, the circular outline, nearest the sun, 

 was perfectly distinct ; the appearance, however, was so tran- 

 sient, that a general description only can be given. 



The straight line joining the extremities of the enlightened 

 segment, would have been nearly at right angles to the path of 

 the centre ; and the illumination evidently was such as would 

 arise from the effects of the solar rays falling on a spherical 

 body, unconnected with any atmospheric medium. (Plate III. 

 Fig. 6) 



At the time of greatest obscuration, the diminution of light, 

 although considerable, was by no means so great as had been 

 anticipated, A mild agreeable lustre was diffused over the 

 nearer objects, and it was only in the deep blue tones of the 

 back ground that one could recognise 



A faint erroneous ray, 



Glanced from the imperfect surfaces of tbings. 

 Fling half an image on the straining eye. 



* M. Le Monnier seems to have nibunderstood this description of Dr. 

 Halley'8, and to have taken for indications of atmosphere, what the latter 

 has as. ribed to the effects of the lunar moimtains,— See Mem. de I'Acad. 

 de.1 Sc'unceH, 1TB I, p. -Ti'^. 



