of long period in the mean motion of the Moon. 189 
well fitted to answer this purpose and compared them directly 
with Hansen’s Tables. 
Th 
ey are 
a Seeritaison of Aldebaran, 1680, Sept. 18, observed at 
Greenwich by Flamstead. 
2. Occultation of the same star 1680, Nov. 7, observed at 
Greenwich by Flamstead, and at London by Halle 
3. Total eclipse of the sun 1715, May 3, obser ved at Lon- 
iat Greenwich and Wanstead by Halley, Flamstead and 
d. 
To compute the occultations of Aldebaran the mean position 
for 1680-0 was derived from Le Verrier’s Tables (Annales de 
l' Observatoire, Tome as correcting the right ascension by 
-++0°-01, and was as follo 
o(1080) = 4 Ss 375-01 
« $16" 49’ 11/8 
The corrections for Pa to ests place are 
for se 2 Ae =—+2°90; Ad=+1" 
Aem+t4-18  Ad=+2°4 
The f slleering oe positions of the moon were derived 
from Hansen's Tables 
Date (Julian C Sept. 13. 
s 
r. Mean Time, 3 50 39 $15 
D's Longitude, [64° 64’ 24”-3|65° 37’ 20/7-4|64° 33’ 117-6 658 91 49""6| 
“ Latitude, |-4 45 29°8 |-4 48 10°6 |-4 39 269 |-4 40 480 
Parallax, 0 59 300 | 0 59 288 | 1 1 185 |1 1 178 
From these data we derive the following times for the im- 
mersion and emersion of Aldebaran for the dates in question. 
The observed times have been concluded from the observed 
altitudes and clock times given by Flamstead in the Historia 
Celestis, kindly furnished me by Prof. Winlock. They differ 
but little from the results of Flamstead himself, when the latter 
are corrected for the equation of time. 
| Computed. | Observed. | c—o. | 
. h m ee s | 
Sept. 13, namisilseiy 15 2 49 15 0 53 +116 
Nov. 7, Tnumers | 
ae | 
ee te ee ee: ee oe 
P  Bbaat ee ee 
(8 eee ie 8 a 8 | 4 es 
The great difference between the results of the two phases of 
the first occultation gives rise to a suspicion of error in the ob- 
servations or the data of reduction. e second observation is 
confirmed by that of Halley in London, he having observed 
the immersion at 7" 50™ 98, a noticed that the star was ‘“new- 
ly emerged” at 8° 47" 1%. lace of observation w 
= twenty-five or thirty Gunde west of Greenwich, and pe eg 
