1882.] On the Conservation of Solar Energy. 393 



tangential velocity of our earth. This high rotative velocity of the 

 sun nmst cause an equatorial rise of the solar atmosphere to which 

 Mairan, in 1731, attributed the appearance of the zodiacal light. La 

 Place rejected this explanation on the ground that the zodiacal light 

 extended to a distance from the sun exceeding our own distance, 

 whereas the equatorial rise of the solar atmosphere due to its rotation 

 could, not exceed -/^ths °^ the distance of Mercury. But it must be 

 remembered that La Place based his calculation upon the hypothesis 

 of an empty stellar space (filled only with an imaginary ether), and 

 that the result of solar rotation would be widely different, if it was 

 supposed to take place within a medium of unbounded extension. In 

 this case pressures would be balanced all round, and the sun would 

 act mechanically upon the floating matter surrounding it in the 

 manner of a fan, drawing it towards itself upon the polar surfaces, 

 and projecting it outward in a continuous disk -like stream. 



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

 posed to be drawn in enormous quantities toward the polar surfaces 

 of the sun ; during their gradual approach, they will pass from their 

 condition of extreme attenuation and extreme cold, to that of com- 

 pression, accompanied with rise of temperature, until on approaching 

 the photosphere, they burst into flame, giving rise to a great develop- 

 ment of heat, and a temperature commensurate with their point of dis- 

 sociation at the solar density. The result of their combustion will be 

 aqueous vapour and carbonic anhydride or oxide, according to the 

 sufficiency or the insufficiency of oxygen present to complete the com- 

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

 of centrifugal force will flow toward the solar equator, and be thence 

 projected into space. 



The next question for consideration is : What would become of 

 these products of combustion when thus rendered back into space ? 

 Apparently they would gradually change the. condition of stellar 

 material, rendering it more and more neutral, but I venture to suggest 

 the possibility, nay, the probability, that solar radiation would, under 

 these circumstances, step in to bring back the combined materials to 

 a condition of separation by a process of dissociation carried into effect 

 at the expense of that solar energy which is now supposed to be lost 

 to our planetary system. 



According to the law of dissociation as developed by Bunsen and 

 Sainte-Claire Deville, the point of dissociation of different compounds 

 depends upon the temperature on the one hand, and upon the pressure 

 on the other. According to Sainte-Claire Deville, the dissociation 

 tension of aqueous vapour of atmospheric pressure and at 2800° C. is 

 0'5, or only half of the vapour can exist as such, its remaining half 

 being found as a mechanical mixture of hydrogen and oxygen, but 

 that with the pressure, the temperature of dissociation rises and falls, 



