SfA WILLIAM SIEMENS, F.R.S. 303 



of the distance of Mercury. But it must be remembered that 

 La Place based his calculation upon the generally accepted 

 hypothesis of an empty stellar space (occupied only by an 

 imaginary aether), and it can be shown that the result of solar 

 rotation would be widely different, if supposed to take place 

 within a medium of unbounded extension. In this case pressures 

 would he balanced all round, and the sun would act mechanically 

 upon the floating matter surrounding him in the manner of a 

 fan, drawing it towards himself upon the polar surfaces, and 

 projecting it outwards in a continuous disk-like stream from the 

 equatorial surfaces. 



By this fan action, hydrogen, hydrocarbons, and oxygen are 

 supposed to be drawn in enormous quantities toward the polar 

 surfaces of the sun ; during their gradual approach they pass 

 from their condition of extreme attenuation and intense cold to 

 that of compression, accompanied with increase of temperature, 

 until, on approaching the photosphere, they burst into flame, 

 giving rise to a great development of heat, and a temperature 

 commensurate with their point of dissociation at the solar density. 

 The result of their combustion will be aqueous vapour and carbonic 

 acid, and these products of combustion, in yielding to the influence 

 of centrifugal force, will flow towards the solar equator, and be 

 thence projected into space. 



In view of the importance of this centrifugal action for the 

 purpose of my theory, the following simple mathematical state- 

 ment of the problem may not be thought out of place. Let us 

 consider the condition of two equal gaseous masses, at equal 

 distances from the solar centre, the one in the direction of the 

 equator, the other in that of either of the poles. These two 

 masses would be equally attracted towards the sun, and balance 

 one another as regards the force of gravitation, but the former 

 would be subject to another force, that of centrifugal action, 

 which, however small in amount as compared with the enormous 

 attraction of the sun, would destroy the balance, and determine a 

 motion towards the sun as regards the mass opposite the polar 

 surface, and into space as regards the equatorial mass. The same 

 action would take effect upon the masses filling their places, and 

 the result must be a continuous current depending for its velocity 

 upon the rate of solar rotation. The equatorial current so pro- 



