ail Sn ae 
ag os 
G. Hinrichs on Planetology. 143 
BCE =, would increase, whilst A and B remain nearly at the 
same distance from C: so that an annular nebula with a central 
core might in time result from a spiral nebula; even severa 
concentric rings might be formed. 
1. 
still would con- 
tinue to be a proximate; the angular velocity would sti 
greatest near the central parts, as can also easily be shown di- 
rectly, by considering the motion of each particle as subject to 
the attractions of all the others. Then the particles originally in 
4 straight line would still in time form a spiral. 
So we see that a nebula originally in the shape of a light ree- 
tilinear cloud with a condensation near the middle, like the part 
in fig. 1, would after some time exbibit a spiral like the dar 
art in fig. 2, The nebuls, Herschel 1061, and IH. 1337, as seen 
y Lord Rosse,’ have exactly such a form. If, instead of having 
the nucleus in the middle, the original nebula had been denser 
near one extremity, like fig. 3, a simple spire like fig. 4 woul 
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be the resulting spiral nebula, as we see it in H. $27, H. 1946, 
Bond, Direct ard College Observatory, kindly sent me 
f Roe by Ses of spiral nebule—for which important 
my sincere thanks. 
