336 
The Great Nebulae 
[ch. XIII 
through the generalised Roche’s model. An alternative way, which lends itself 
to convenient discussion is through the series of adiabatic models discussed in 
§ 235. Roche’s model is represented by taking k — 1*2, the incompressible 
model is obtained by taking k= oo, and the bridge is formed by allowing k 
to vary continuously from 12 to oo. 
Fig. 55. 
Again we obtain a series of elliptical figures, which gives place when 
k < 2 2 to a series of pseudo-spheroids with rings of matter in the equatorial 
plane, and gives place when k > 2 2 to a series of pseudo-ellipsoids, with two 
streams of matter shed from the ends of the longest diameter. 
The general series of configurations which have been obtained, as the fruit 
of the theoretical research summarised in Chapter ix, may be represented 
VA 
Fig. 56. Roche’s Model. Fig. 57. Adiabatic Model. 
Figs. 56 and 57. Diagrams representing theoretical configurations of Rotating Masses. 
diagrammatically as in figs. 56 and 57. Fig. 56 refers to the generalised 
Roche’s model, v^/vj, denoting the ratio of the volume of the nucleus to that 
of the atmosphere. Fig. 57 refers to the adiabatic model, k denoting the index 
which occurs in the law p oc p K . 
The general arrangement of series of configurations presented by these two 
models is seen to be very similar. Perhaps, however, this is hardly surprising