W. A. Norton on the Dimensions of Donati’s Comet. 65 
through the foregoing calculated positions, and is accordingly 
the outline of the train, as theoretically determined. The por- 
tion of the train represented extends about 104°, or 10,000,000 
miles from the nucleus. The scale of the diagram is too small 
: yt 
R. Asc,, 212° 3 40”, Dec. 19° 39'11” N.) The consequence is 
that the theoretical falls behind the actual train. 
he following table gives the distances of the foregoing calcu- 
lated positions of particles from the contiguous outline of the 
tail. The positions are all behind the observed outline. 
Particle 
left Oct. 226043. '8 902-720! @ent 947-000 & pt. 24¢'360| Sept. 194-049|Sep 122-224 
nucleus, | nz re ; Paes 
Force. jLat. vel] Dist. Da 1 oe ol Date SL) Da. Lope: 
ae ‘ 1 i 
R,t213/40:255| area 25-4 22:8 18 ; 
A,0 4951-07184 18: 25:4 86 | 47 
The calculated positions are indicated by dots in the diagram, 
If they be taken in pairs, on opposite sides of the train, it will 
be seen that the lines connecting them are approximately per- 
pendicular to its general direction. The lengths of these lines, or 
he approximate breadths of the train, at the several points, as 
Compared with the lengths of the lines traversing the actual 
train, in parallel directions and at corresponding distances from 
1 
_ the nucleus are given in the following table: 
- 29a" Sept. 2649 Sept. 24a°3. 
Particles left nucleus, tage ppp se : ee and | 
Sept. 29¢-7, Sept. 24:3. Sept. 192.0 Sept. 13-43. 
i 
Caleulated lengths| 14/5 37°9 85:8 168°6 
|Actual Megihs: 16°5 35:2 86:4 1'70°7 
the number of minutes in the arc ween a the a gd 
or in the corres onding arc traversing the observed train. 
The broken fine lying nearly in the middle of the gener 
train, is traced through the positions occupied by the sever: 
Particles which left the nucleus at the assumed dates : 
Au. Jour, Sct.—Srconp Serims, Vou. XXXII, No. 9—Jury, 186 
9 
