2^ On the Solar Eclipse, 



portion of the lunar circumference produced a very singular 

 and pleasing effect, their summits frequently appearing to 

 impinge as it were upon the sun, shewing like angular incisions 

 in the margin of his lower limb, before the adjacent and less 

 elevated parts of the moon's periphery had as yet made any 

 impression on his disc. Small and imperfectly angular inter- 

 stices also were thus formed between the points of appulse in 

 the two luminaries, through which coruscations of the solar 

 rays were seen to dart at intervals, sometimes with a faint pur- 

 plish light, at others with a dark red or dusky splendour, but 

 without any regularity in the alternations. This distinction, 

 however, was invaribly observed, that the intensity of the colour 

 increased in the inverse ratio of the angle formed by the ray, 

 and the plane of the moon's darkened hemisphere ; that is, the 

 more acute the angle at which the ray fell into the penumbra, 

 the greater was the brilliancy of its light. To these appearances 

 reference hereafter will be made ; at present, it is sufficient to 

 remark their agreement with what M'Laurin mentions respecting 

 " the light breaking into irregular spots near the point of con- 

 tact during the formation of the annulus" in the eclipse of 1737 ; 

 also with Dr. Halley's statement " of flashes of light darting 

 from behind the moon" in that of 1715. And in general with 

 similar appearances described by later observers, although the 

 present observations, as will afterwards be shewn, seem to war- 

 rant a different explanation from that which is commonly 

 received. 



Of these lunar mountains some appeared to be disposed in 

 connected chains of great extent, which at one extremity gene- 

 rally terminated abruptly, inclining from the perpendicular by 

 a very acute angle ; but in the opposite direction their altitude 

 diminished by degrees, gradually subsiding to the common 

 level of the moon's circumference. Another division consisted 

 of mountains apparently solitary and detached, and which 

 seemed to rise suddenly from the surface of extensive plains, 

 with a form almost regularly conical, as far at least as could be 

 judged from the gradual inclination of the sides exposed to 

 view. In these isolated mountains likewise every gradation 



