450 ES ee Re Motion of the T: mies Nebula M. 20. 
and so continues up tol. That is, the line 12-13 is involved in 
the fainter nebulosity. 
III. The line 14-20 cuts off the canes borders of A, but is 
involved only in fainter nebulosity. .It is, however, about tangent 
to the brighter nebula about 1, 2, 19. 
IV. The line 10-1 prolonged i is involved in A preceding 1. 
he line 35-3 is almost exactly parallel to the line 12-13 
es and intersects A near the triple star. This line is 
tangent very exactly to the Bre edge of the brighter 
nebulosity about these three star 
We may make the following summary of the evidence with 
Sate to the position of the triple star relative to the 
nebulosity. 
the very ed e of. , but in Mason’s figure ant in his notes, 
ee Certain,” he places these stars within the nebula, and 
ably a meet of the two memoirs will result in the 
sere that Mason was right mh that we must suppo 
the triple star to have been involved in 1837-9. It is all the 
1 
more proper to come to this aenelanon as Herschel does not ex- 
ss 
to be noted here that this position is utterly different from the 
one derived from thesevidence of the earlier observatio 
In the absence of satisfactory micrometric measures ionic 
indeed are almost impossible to make on this point even with 
bei Sounenetig wires), it may be said that Lassell’s (2 fig- 
ures), Trouvelot’s and my own observations agree in this re- 
spect with Mazon’ 8, rallowhig for difference of telescopes. We 
may therefore say with certainty that— 
%. From 1839 to 1877 the triple star was not centrally oleae’ 
between the three nebulosities, but was involved in A. The 
ve 
same time it must be noted that’ in several respects these observa- 
tions vary from other later ones, and it is to be remembered that 
the evidence is _— mostly derived from verbal and definite de- 
scriptions, an erefore are of greater weight than if deduced 
II. The line 12- 13, according to Herschel, does not intersect 
ason—does not intersect ‘A; Lassell ( (1)—does intersect A ; 
Lassell (2)—does intersect 4; Lan ngley—does not intersect A; 
Trouvelot—does not intersect A; Holden—does intersect 
