306 L. Boss—Tail of Comet b, 1881. 
TABLE I, 
Nuclens. Axis, right-line tail Curved tail Point 
“4 8 a Fy i F ih okey tail 
June 26, 135 30™ 8:21 6S | S18" 83°°0 99° |.80°°5 Axis. 
ks rnd icp cece 13°2 A eee a ob hai 
June 28, 13" 00 90°1 63°9 20° 85°9 | 155 86-0 Axis. 
oie chy pte saute ear loe 83°0 is. 
July 1, 128 15m 95-8 | 70°7 ein .--. |111:2 | 87:0 | Pree. edge. 
Pe CaM R ae ...- |115°3 | 80°0 | Foll. edge. 
July 22, 145 00 177-6 819 215°4 82°8 | 205-0 82°2 i 
It would have been better, no doubt, to have made no 
special effort to determine the position of the extreme Mat 
limit of the tail, but to have given greater. attention to t 
position of the axis and the bre adth of the visible portions a 
points where the tail could be easily seen. But even with the 
present imperfect data, we shall be able to derive some idea of 
the real position of the tails in space, and of their correspond- 
ence in type with others which have been observ ed. 
Conv enlent formule have been devised by Bessel (Astr. 
r= Radius vector of the Pes i the time of Sila atiol 
p=Geocentric distance of n 
A=Length of tail, or eration of point observed from the nucleus. 
s= Angular length of tail. 
Pp =Position angle at the nuclens of r prolonged. 
p=Corres ponding angle for the observed point in the tail. 
S=The cometocentric —" of the earth from the ernst pole 
the comet’s or 
T=Cometocentric angle en the earth and the observed 
point in the tail. 
y' =The cometocentric angle between the observed point and the 
dius vector prolonged,—positive, when this point is on 
that side of the radius vector from which the comet has 
been moving. 
From the elements of Dr. Oppenheim (Astr. N., 2384), we 
find for the codrdinates of the north pole of the orbit of comet 
b, referred to the equator, 
A=192° 09”. D= 423° 467. 
