25 (i 



OBSERVATIONS OF THE ECLIPSE 



The irregular decrease and increase of the distances between 

 the points of the cusps, is greater than would arise in. so ex- 

 cellent a micrometer from the small imperfections inseparable 

 from such observations. These irregularities were principally 

 occasioned by the uneven surface of the moon, particularly 

 that part, which formed the southern cusp or horn. — The 

 northern cusp was well defmed, and finely terminated, but the 

 southern one was sometimes obtuse, at others terminated by a 

 parallel thread of light, which disappeared from one end to 

 the other, at the same time; and frequently one or two lumi- 

 nous points of the sun's limb, were observed to be completely 

 detached from the point of the cusp. — The most remarkable 

 of these phenomena was observed between 10 h 52', and 10 h 55'. 

 To give some idea of this appearance, let the circle ABCD 

 Fig. 2d, PI. VI. represent the periphery of the sun's disk, and 

 EBFD that of the moon's: the line EAFC a vertical, supposed to 



