if the Sun did not rotate, we could only expect radial convection 
currents. But the rotation of the sun completely changes this form 
of motion; the angular velocity of descending masses increases, of 
ascending masses diminishes; there will be found side by side gas- 
layers of different densities, and rotating at different speeds. 
It has been shown by von HermHorrz, that during a certain time 
such gaslayers can flow side by side, sharply separated by a so-called 
surface of discontinuity (i.e. by a surface, on passing which the 
values of the velocity and the density change with a leap); but 
gradually the friction causes this surface to undulate; the waves 
advance with the more swiftly moving layer, they grow steeper, 
overhang and break, forming whirls; and thus, by the mingling of 
the adjacent parts of the two layers a new layer is formed between 
them, the properties of which will be intermediate between the cor- 
responding properties of the original layers. 
From the conditions of the problem we may deduce the position 
of the surfaces of discontinuity. This has been performed by von 
HerrmHoLtz with regard to the air-currents in our atmosphere, and 
by Emprn for the rotating layers of the Sun. He arrives at the con- 
clusion, that in the Sun the surfaces of discontinuity must in the 
main have the shape, figured in the accompanying sketch and reminding 
us of hyperboloids of revolution *). 
N 
a“ 7 ED . 
7 N 
\ 
/ \ 
H \ 
Aequ ator 
‘ | 
/ 
\ / 
4 
SS a“ 
Fig. 1. 
1) EmpeN draws the intersections of the surfaces with the plane of the paper 
only inside the circle, representing the sun’s boundary. | have dotted this circle, 
with a view to indicate, that the border is only a seeming one; accordingly | 
prolonged the intersections outward. 
