W. A. Norton on the Dimensions of Donati’s Comet. 63 
‘e Distance. ae } 
Average Inc." 3-93 IR, 1°82 R, 1-213R, 0455 JA, 0303 JA, 0-455 
} } 
2°6043|-11 4o 45 | -0-25 , | + ; ; ; 
° o80 | -0°43 | -0:25 | -o-ar | ~0-33 
Sept. 24-360 [+ 6 16 12 -0'63 | +264 | -0°84 ie 
; | =3'73 | +142 
{ +073 =-TII 
Sept. 13°834 |+27 35 o 
These results show that all the cometary particles which may 
have been repelled from the nucleus in the line of the radius- 
vector, at any instant of time, and may have become widely sep- 
arated by reason of the unequal repulsive actions of the sun upon 
the different particles, would be found distributed approximately 
along a right line directed toward the nucleus. If we consider a 
Jet of cometary matter streaming out from the nucleus under an 
angle to the radius-vector, all of its particles, variously influenced 
by the sun, are found at the assumed date (Oct. 54-0776), distrib- 
uted nearly along a line diverging somewhat from the line of the 
particles ejected at the same instant from the nucleus directly to- 
ward the sun. It lies in advance of the latter line in the case of 
& jet emanating from the preceding side of the nucleus, and be- 
hind it in the case of a jet proceeding from the following side. 
The entire collection of matter proceeding at any instant of time, 
m the various points of the side of the nucleus*turned toward 
the sun, which lie in the plane of the orbit, accordingly forms, 
a8 It flows off into space, a band of nebulous matter, the sides of 
which are somewhat. divergent, and the general direction of 
Which is toward the nucleus. The entire train of the comet 
may be regarded as made up of a series of such bands of comet- 
ary matter which left the nucleus at various points of time ante- 
tior to the time of observation. Unless the ejection of matter 
was Intermittent, these bands would be infinite in number, and 
Overlap each other. If there were interruptions of continuity in 
the outflow of matter, they might become separately discernible. 
The following are the calculated positions of particles which 
scem to accord most nearly with the position and form of the 
“onvex side of the train, as actually observed: 
ie 
saat Oct. 22°6043, Sept. 290°7523, | Sept. 267-9003. Sept. 24¢°360. 
—_o——.. 
Force. |Lat.vel| Ro Asc.) Dec. |B. Ase. | Dee. | ned Dec. "| R. Asc. | Dee. | 
Biases! cake nd 4 uw) 0 in| 0. af ae Pd Oo, 1 H\e ul o wu} ou u 
T | 20]20 2 90/21 9 | 
The lateral velocity here assumed, answers to a jet emanatin 
is the preceding aida of the nucleus, under an angle of 19° 
to the radius-vector, (see p. 58). ee 
The concave, or hllowhng side of the tail is best represented 
by the following calculated positions: ; 
