SCIENTIFIC SUMMARY. 
305 
1864 
1865 
1866 
1867 
1868 
1869 
v. 6'-87 
6'-26 
5 / -64 
5'-25 
6'-58 
8'-39 
v'. 6'-00 
6'-72 
5'-70 
5'-69 
6'*65 
7' -82 
The accordance is close enough to indicate the truth of the general prin- 
ciples on which the Professor’s formula is founded ; but it is also clear that, 
with the progress of observation, the coefficients of the formula will have to 
be altered. 
The Periods of Certain Meteoric Pings. — Professor Kirkwood has made 
another of his careful studies of meteoric and cometic phenomena. Com- 
paring the period of the first comet of 1861 with the dates on which the 
most remarkable displays of the April meteoric shower have taken place, 
he shows that there are fatal objections to the hypothesis suggested by Dr. 
Weiss, that the comet and the meteors may be in some way associated. 
Continuing the inquiry, he shows further that the period of the meteors is 
probably about 28^ years, the major axis of their orbit about 18-59 (the 
earth’s mean distance as unity). Thus the distance of the aphelion is nearly 
equal to the mean distance of Uranus. He notices that the meteors of 
December 11-13 seem to have a period of about 29^- years; those of 
October 15-21 a period of about 27J years. He adds, “ If these periods 
are correct, it is a remarkable coincidence that the aphelion distances of 
the meteoric rings of April 18-20, October 15-21, November 14, and 
December 11-13, as well as those of the comets 1866 I. and 1867 I. are all 
nearly equal to the mean distance of Uranus.” 
The Period of Algol. — Mr. Penrose has lately observed the epochs when 
this star has been at its minimum of brightness. His observations, which 
represent the phenomena certainly within 10 minutes, show that the period 
of 2-86727 days, which has been assigned to the variation of this remarkable 
star (combined with an epoch given for January 3, 1844), requires a slight 
correction ; for the minima observed by Mr. Penrose occurred nearly three 
hours earlier than if due to those data. He assigns the period 2-867234. 
It may be that the change of period referred to by Sir John Herschel as 
actually in progress may account for the observed discrepancy. 
The Planet Saturn. — Saturn is the only planet which will be well situated 
for observation during the ensuing quarter. 
Total Lunar Eclipse. — There will be a total eclipse of the moon visible at 
Greenwich on the night of July 12, 1870. The following table gives the 
epochs of the principal phases. 
First contact with the penumbra July 12 
First contact with the shadow . ,, 
Beginning of total phase ... „ 
Middle of the eclipse .... „ 
End of total phase „ 
Last contact with the shadow . July 13 
Last contact with the penumbra . „ 
7 46-0 p.m. 
8 44-6 
9 44-4 
10 34-2 
11 240 
0 23-8 a.m. 
1 22-4 
4 At the middle of the eclipse the earth’s shadow will extend beyond the 
totally eclipsed disc of the moon to a distance of 0-675, the moon’s apparent 
diameter as unity. 
YOL. IX. — NO. XXXYI. 
X 
