Mr. J. Gill on the Dynamical Theory of Heat. 373 



may have an end ; though the certainty of the prospective eter- 

 nity of our spiritual existence is gladly acknowledged by the 

 wisest and the best, and it is difficult to conceive of the anni- 

 hilation of even common matter. It is probable that our planet 

 has already undergone changes the nature of which may never 

 be clearly revealed to human intelligence; and whenever the 

 great catastrophe may occur which is to change the present order 

 of terrestrial existence, is it not probable that the agencies em- 

 ployed, though not opposing or inverting natural law, may still 

 differ essentially from the ordinary routine of physical phenomena 

 which, with a continual rotation of periodic change, conveys the 

 idea of general cosmical permanence ? 



Analogy would indicate the probability that the planets may 

 be receiving from the sun something more than mere motion, or 

 radiant heat and light, as generally described, and the idea is not 

 perhaps without support from physical facts. The vital solar 

 fluid which reaches the earth may become, as it were, analyzed 

 and assimilated in the various active processes of nature by 

 which organisms are built up ; whilst, besides radiant heat, there 

 is emanating from the earth into space a current of comparatively 

 effete cosmical matter which joins the general effluent solar tide, 

 carrying with it part of the vis viva of the terrestrial molecular 

 motion which we call heat, and another portion of this heat is 

 transferred by the universal aether, in the act of radiation, to the 

 solar tide. The accumulation of molecular motion on the earth's 

 surface is thus prevented by a continual change into the vis viva 

 of the motion of translation of the effluent particles, which, with 

 the general solar tide in their outward progress, go on changing 

 this vis viva into potential energy of centripetal gravitation. 



There is reason to believe that the idea of a universal ocean of 

 interstellar sether has been entertained from the remotest times 

 of physical speculation ; and this idea still prevails, being sup- 

 ported by a strong preponderance of probability. The undula- 

 tory theory of light shows that the mighty pulse of this cosmical 

 vital fluid is beating throughout the universe at the amazing 

 rate of four hundred and seventy-four millions of millions of 

 strokes per second ! All these pulsations are caught by the 

 delicate optical mechanism of the eye in a single second, and 

 the resulting impression is that of light. From this single mani- 

 festation some faint idea may be conceived of the wonderful pro- 

 perties which should characterize this cosmical fluid. As com- 

 pared with terrestrial matter, it is supposed to be imponderable 

 and comparatively non-resisting, and to be universally present. 



It is known that the sun has an atmosphere containing in a 

 state of vapour or gas several substances which exist on our 

 planet in a solid form. How far may the solar atmosphere be 



