64 NOTICES OF THE MEETINGS [May 2, 
and 1851: (the former being from W. S. W. to E. N. E. nearly, 
the latter from N. W. to S. K. nearly). This arose in part from 
the circumstance that (as above explained) the former of these eclipses 
occurred when the node or end of the intersection-line of the planes 
of orbits, turned towards the July sun, was that at which the moon 
rises to the north of the ecliptic, the latter when it is that at which 
the moon is descending to the south of the ecliptic. But the prin- 
cipal cause of the difference is this ; that the former eclipse occurred 
early in the morning, the latter in the afternoon: on placing a 
terrestrial globe in the proper position for July, with its north pole 
inclined considerably towards the sun, it is seen that, even if the 
moon moved precisely in the ecliptic, the path of her shadow across 
Europe before Europe came to the meridian would trend from the 
south to the north ; but if Europe had passed the meridian it would 
trend from the north to the south. 
Quitting the geometrical explanations, the Lecturer then pro- 
ceeded to describe some peculiar phenomena which had been observed 
in eclipses, and first, one which had been observed most distinctly 
in annular eclipses, and which is known by the name of ‘‘ Baily’s beads 
and strings.’ When the preceding limb of the moon, traversing the 
sun’s disk, approaches very near the sun’s limb, or when the following 
limb of the moon is in the act of separating from the sun’s limb to 
enter on the sun’s disk, the two limbs are joined for a time — (no one 
has estimated the duration with accuracy)— by alternations of black 
and white points or strings. Phznomena, evidently of the same class, 
have been observed in the transits of Venus and Mercury over the 
sun’s disk; the black planet, when just lodged on the sun’s disk, being 
pear-shaped, with its point attached to the black sky. The Lecturer 
was able to state, in his own experience at the Royal Observatory, 
that at the same transit of Mercury this phenomenon was seen 
with some telescopes and was not seen with others. In the annular 
eclipse of 1836 observed at Kénigsberg, where the moon’s limb but 
just entered completely on the sun’s, and where consequently it 
grazed along the sun’s for many seconds of time, the phenomenon 
appeared to resolve itself simply into points of light seen between 
lunar mountains. The Lecturer expressed himself generally satisfied 
with Professor Powell’s explanation, that the phenomenon originates 
in that inevitable fault of telescopes and of the nervous system of the 
eye which tends to extend the images of luminous objects (producing 
what is generally termed irradiation), and thus enlarges the sun’s 
disk towards the sky, towards the moon or planet, and towards the 
bottoms of its hollows. 
In describing the total eclipse of 1842 (which perhaps was better 
observed than any one preceding it) the Lecturer insisted on our obli- 
gation to M. Arago, who had prepared the preliminary notices, and had 
used his powerful personal influence in inducing persons to make ob- 
servations at numerous stations in the south of France; and had 
afterwards collected and compared the observations. Besides these 
—— 
