80 Chronicles of Science. [Jan., 
of the umbra, which gradually softened off into the penumbra. The 
truncation of thecones of the umbra and penumbra is seen in per- 
spective as well-marked ellipses. 
Picture No. 11, 10h. 41m. 17s. (exposure three seconds), a 
little later than the middle of the eclipse, which occurred 1m. 42s. 
earlier. The obscuration of the umbra and penumbra extends in a 
curved line, commencing in their visible effects on the photograph 
at the parallel of 15° south latitude on the western limb, passing 
over Langrenus, Goelenius, Guttemburg, Capella, Theophilus, Kant, 
Dollond, ‘Albategnius, Ptolemeus, Parry, Bonpland, Euclides, above 
Flamsteed, and passing over the southern limb of Grimaldi, above 
the parallel of 10° of south latitude. 
Picture No. 16, 12h. 54m. 12s., was exposed exactly one 
minute, ending at the above-named time; the unobscured portion 
of the moon was completely solarized, and the details in conse- 
quence lost; yet not the shghtest trace of any part of the lunar 
disk was depicted within the limits of the umbra. The next picture 
was instantaneous, the expostire certainly being less than a quarter 
of a second, yet the whole of the unobscured surface is clearly 
though faintly depicted. 
The Astronomer Royal has published a long paper on the value 
of the moon’s semi-diameter as obtained by the investigations of 
Hugh Breen, Esq., from occultations observed at Cambridge and 
Greenwich. 
A proposal having been made by Mr. Breen to extend the re- 
duction of the occultations observed at Greenwich, it was suggested 
by Professor Airy that the occultations, in their reduced form, as 
exhibited in the ‘Greenwich Observations,’ might be used for the 
determination of the semi-diameter of the unilluminated moon. Mr. 
Breen accepted this suggestion, and the Admiralty sanctioned the 
undertaking and supplied the necessary funds. Mr. Breen detet- 
mined on applying his computations to the occultations observed at 
the Cambridge Observatory during the Astronomer Royal’s presi- 
dency over that Institution, ending with 1835, and to those ob- 
served at the Greenwich Observatory from 1836 to 1860. 
Mr. Breen originally included in his computations the oc- 
cultations of every class. But viewing the causes of inaccuracy 
of various kinds attending the occultations of planets—the un- 
certainty of the planet’s place for the day, the uncertainty of the 
planet’s semi-diameter, the difficulty of correction for phase and the 
general rudeness of the observation—it was thought best to strike 
out the planets and to confine the investigations to stars. 
The results were divided into four classes :— 
I. Disappearances of Stars at the Dark Limb; II. Disappear- 
ances at the Bright Limb; III. Reappearances at the Dark Limb; 
IV. Reappearances at the Bright Limb. ‘The following are the 
