The Conservation of Solar Energy 2 1 9 



these are capable of being dissociated by radiant solar 

 energy, (3) that they are then drawn towards the sun in 

 -consequence of its rotating velocity, impinging on its polar 

 surface and passing away again into space at its equatorial. 

 Thus the dissociated material on approaching the solar 

 photosphere would flash into flame, and in passing from 

 the polar to the equatorial region it would give rise, through 

 mixture with the lower and heavier solar atmosphere, to 

 vortices and sunspots. The gases, which passed away 

 ^quatorially, would consist of products of combustion, which 

 at last would be sufficiently rarefied to be again dissipated 

 by the radiant solar energy. By this theory zodiacal 

 light, the appearance of comets, and the aurora borealis 

 might be reconciled. 



Sir W. Grove said that, even assuming the postulates, he 

 could not accept the conclusions ; for it would appear that 

 the force given off from the sun, after expending itself in 

 producing certain changes in matter, would return to the 

 sun and add to its heat that is, to its energy which had 

 been already expended. Professor Dewar objected that 

 as dissociation varied chiefly as a function of the tempera- 

 ture, and was only affected within narrow limits by alteration 

 of pressure, it had yet to be proved that extreme rarefaction 

 of the gases would suffice to render them capable of being 

 dissociated by the radiant solar energy. 



March 23rd, 3i4th meeting. In reference to Dr. Siemens's 

 communication to the last meeting, Dr. Debus expressed 

 doubts whether an action, such as the sun had been supposed 

 to exert on gases and vapours, could rightly be termed 

 dissociation. This gave rise to a discussion, in which 

 Professors Dewar, Frankland, and Odling took part, and it 

 was the general feeling that though there were precedents 

 for using the term as Dr. Siemens had done, decomposition 

 would be the more appropriate. 



Mr. Galton quoted a statement from a newspaper to show 

 the loss of radial energy in sunbeams as they pass through 

 the lower atmosphere. A party, which ascended the 

 Schilthorn (9747 feet) on a bright day in the depth of winter, 



