64 W. A. Norton on the Dimensions of Donati’s Comet. 
Bis _194-0490. 
_R. Asc, Dec. 
we Re 
52 10125 9 20 
Sept. 137834. 
R. Ase, _ Dec. 
1 
28 37 50 
Left nucleus. 
acl Sept. 297°7523. | Sept. 240360, 
Force. _ Lat. vel. 
_R. _ Asc. Dec. R. Asc. | Dec. 
iar3 55 we 4 at 
A, 0°455} 
It will be seen, in a zack part of the discussion, or the 
maximum lateral velocity for particles proceeding from the fol- 
nek side of the nucleus, and which may, because of the feobler 
epulsions they experience, be afterwards found at the concave 
e of the tail, cannot well exceed 0™-18; but may be less. 
re it would seem, without going into a detailed Seeneets 
that the concave outline of the tail, for the extent of it un 
consideration, might be about as well represented by assuming - 
smaller initial lateral velocity and. increasing somewhat the 
effective attractive force of the sun. - I find, by estimation from 
~0-184 ars af Sola0" 16:40 214 $30 
tail — on his, whole, be pretty well represented by Aeoeaa 
the supposed lateral velocity (0™255) and augmenting the Jimit 
of the solar repulsion. The value of this limit thus obtained is 
about 15. It is importa nt to observe, however, that at mode- 
rate distances from the nucleus the breadth of the train was 
much paeier than these limits, with a lateral velocity equal to 
ro, give; and that the observed breadths at such’ distances 
afford ind ubitable evidence of the existence of considerable lateral 
velocities imparted, at the outset, by the action of the nucleus. 
ig. 2 will serve to illustrate ‘the comparison of the tail thus 
theoretically determined with the tail as actually observed at the 
2. 
213° 
gem 
eee ‘ 
woe i 
onl 
- 
o 
sae i 
Pe 
oe. rt 
i. " 
216° ae : 
ae ie eto 
- as : 
aa U (pee ET 4 
ot : a a 1 
mi ‘ —— ) 
ead ; 
4+ : 
can H ' 
NE S ea SE BRE ILS. oS 
wie = ~~ ; = 
, —— 
30 250 29° 
same date. The figure of the comet, with os train, which is 
farthest in advance, and whose outline is indicated by a dotted 
curve, represents the same in its actual position and dimensions, 
