40 SCIENCE IN SHORT CHAPTERS. 



matter is afterwards reclaimed and passed over to the polar 

 regions of the sun. This interchange he describes as 

 effected by the differences of pressure on the fluid envelope 

 of the sun; the portion over the polar regions being held 

 down by the whole force of solar gravitation, while the 

 equatorial atmosphere is subject to this pressure, or attrac- 

 tion, minus the centrifugal impulse due to solar rotation. 

 He maintains that this "centrifugal action, 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." 

 He adds that "the equatorial current so produced, owing 

 to its mighty proportions, would flow outwards into space, 

 to a practically unlimited distance." 



I will not here discuss the dynamics of this hypothesis ; 

 whether the reclaiming action of the superior polar attrac- 

 tion would occur at the vast distances from the sun supposed 

 by Dr. Siemens, or much nearer home, and produce an 

 effect like the recurving of the flame of his own regenera- 

 tive gas-burner ; or, whether he is right in comparing the 

 centrifugal force at the solar equator with that of the earth, 

 by simply measuring the relative velocity of translation irre- 

 spective of angular velocity. I will merely suggest that in 

 discussing these, it is necessary, in order to do justice to 

 Dr. Siemens, to always keep in mind the assumed condition 

 of an universal and continuous atmospheric medium, and 

 not to reason, as some have done already, upon the basis of 

 a limited solar atmosphere with a definite boundary, from 

 beyond which particles of atmospheric matter are to be 

 flung away into vacuous space, without the intervention of 

 all-pervading fluid pressure. 



It is evident that if such fan action can bring back all 

 the material that has received the solar radiations, and which 

 holds them either as temperature or otherwise, the restora- 

 tion and perpetuation of solar energy will be complete, for 

 even the heat received by our earth and its brother and 

 sister planets would still remain in the family, as they would 

 radiate it into the interplanetary atmospheric matter sup- 

 posed to be reclaimed by the sun. 



