ON THE ORBIT-ELEMENTS OF COMET I., 1880. 39 
certainty by a careful examination of what is recorded of the older 
comet. Locating on a celestial chart the situation of the head 
concluded from the direction and appearance of the tail, when only 
that was seen, and its visible place, when mentioned, according to 
the descriptions given, it has been found practicable to derive a 
rough orbit from the course thus laid down ; and this agrees in all 
its features so well with that of the modern comet as nearly to 
remove all doubt on the subject. Comets, moreover, are recorded 
to have been seen in A.D, 268, 442-3, 791, 968, 1143, 1317, 1494, 
which may have been returns of this, since the ‘period above men- 
tioned would bring round its appearance to the years 268, 443, 
618, 793, 968, 1143 1318, and 1493, and a certain latitude must 
ways he allowed for aaknown perturbations. But this is not the 
only comet on record whose identity with the comet of 1843 has 
been maintained. In 1689 a comet bearing a considerable resem- 
blance to it was observed from the 8th to the 23rd of a slotiabte 
o is 
this period calculated backwards from 1843-156 will seth us upon 
& series of years remarkable for the appearance of great comets, 
paced of which, as well as the imperfect earings rea we have of 
ir appearance and situation in the heavens, offer t least no 
ais contradiction to the supposition of their identity ‘with this. 
Besides those already m Since as indicated ke the peri mm “e ie 
years, we may specify as probable or possible intermediate 
of the comets of 7 33(2), 1689 above serena") 1559(1) 
1537, 1515, 1471, 1426, 1405-6, 1383, 1361, 1340, 1296, 1274, 1230, 
1208, 1098, 1056, 1034, 1012, 990, 925(0),  858(), 684, 852,530, 121, 
"Should this vie bjec 
pati or oF 247, 180, 158. 
may expect its return about the én of 1864 0 or rlercichad 
of "1865, in which event it it will be observable in the southern 
dnc the ‘‘Cométographie,” a work indispensable to all who would 
