PORTION OF THE COSMOS. COSMICAL SPACE. 35 



by Aristotle), in regard to the former, of self-luminosity. 

 The upper fiery atmosphere of Empedocles is expressly 

 called "bright beaming" (irapQavAiav) , and in certain pheno- 

 mena was supposed to be seen by the inhabitants of the 

 earth as the brightness of fire through clefts and rents 

 (xaff/^ara) opened in the firmament. ( 66 ) 



In the intimate relations between light, heat, electricity, 

 and magnetism, now so much examined, it is deemed pro- 

 bable that, as the transverse undulations of the space-filling 

 ether produce the phenomena of light, so thermic and electro- 

 magnetic phenomena depend on analogous kinds of motion 

 (currents). Great discoveries on these subjects are no 

 doubt reserved to future times. Light, and radiant heat in- 

 separable from light, are, to the non-luminous cosmical 

 bodies, and to the surface of our own planet, a principal source 

 of motion and of all organic life. ( 67 ) Even remote from 

 the surface, in the interior of the crust of the earth, the heat 

 which penetrates inwards calls forth electro-magnetic cur- 

 rents, which exercise their exciting influence on combina- 

 tions and decompositions of substances, upon all formative 

 activity in the mineral kingdom, and on the disturbance of 

 equilibrium in the atmosphere, as well as on the functions of 

 vegetable and animal organisms. If electricity moving in cur- 

 rents developes magnetic forces, if, according to an earlier 

 hypothesis of Sir William Herschel, ( 68 ) the sun itself is in 

 the condition " of a perpetual Aurora" (I should say of an 

 electro-magnetic storm), it would not appear an inappropriate 

 conjecture to suppose that in space also, the light of the sun, 

 propagated by vibrations of the ether, may be accompanied 

 by electro-magnetic currents. 



It is true that in terrestrial magnetism direct observation 



