486 Proceedings. 



world we inhabit ; and the grand conception is that the earth, the planets, 

 and the sun, are all under a law of transition. This is the lumen siccum 

 which is diffusing its rays all around — developing the most astonishing 

 revolutions in natural philosophy. Well may men like Tyndall and Spencer 

 rejoice in lofty labours. 



The heat on the sun's surface is so intense that the elements of compound 

 bodies are torn apart by its destructive energy. The chemical union between 



* 



oxygen with iron, magnesium, calcium, etc., is over-mastered. Both gas and 

 sublimed metal rise into the higher regions of the sun's atmosphere; the 

 metals carry with them in their vapourous state enormous supplies of latent 

 heat, absorbed from the molten surface of the sun. In the higher and less 

 heated regions of the sun's photosphere the atoms of oxygen and metals are 

 againbrought within the powers of chemical forces, and by their mutual attraction 

 clash together in fixed proportions, forming there the incandescent willow-leaf 

 forms of Nasmyth. These, in their condensed form, dart into space heat, light, 

 and electricity ; their latent heat becomes sensible j and they sink again to the 

 surface of the sun, again to gather up fresh stores of heat and light, again to 

 rise up to the upper regions of the sun's photosphere, to be there again subject 

 to the forces of chemical aflinity, and in their hot conflict to be the immediate 

 source of radiant heat and light, and so on through countless cycles, radiating 

 into stellar space the sun's almost exhaustless supplies of heat, light, and 

 electricity. 



The younger Herschell speaks of these feculse, or willow-leaf forms, almost 

 with an abuse of the imagination, as amazing organisms partaking of the 

 nature of life, each not less than 1000 miles in length, whose fiery constitu- 

 tion, as Proctor remarks, " enables them to illume, warm, and electrify the 

 whole solar system. Truly Milton's picture of him who in the fires of hell 

 lay floating many a rood, seems tame and commonplace compared with 

 Herschell's conception of these floating monsters." 



These marvellous displays of chemical forces cannot possibly have been 

 equally intense in all ages, and there is a possibility that the glacial epoch was 

 the result of diminished intensity of the forces in operation in the sun. 



Next, as to the heat from the body of the earth itself. I have not without 

 a purpose alluded to the astounding fact made known by the spectroscope, 

 that the sun is composed of the same substances as those which form the 

 earth. And I now wish you to admit the probability that those forces which 

 are in activity in the sun were once in a like activity in the planets, our 

 earth, and the moon ; and that our earth is in an intermediate stage between 



the moon on the other. In the moon the 



and 



exhausted 



Every change arising out of chemical com- 



binations is completed, and with that completion all further displ 



