RESULTS AND LIMITS OF SCIENTIFIC METHOD. 447 



mately fixed by scientific inference. It is progressing 

 towards a state in which the available energy of 

 matter will be dissipated through infinite surroundino 

 space, and all matter will become cold and lifeless. This 

 constitutes, as it were, the historical period of physical 

 science, that over which our scientific insight may more 

 or less extend. But in this, as in other cases, we have 

 110 right to interpret our experience negatively, so as to 

 infer that because the present state of things began at 

 a particular time, there was no previous existence. It 

 may be that the present period of material existence is 

 but one of an indefinite series of like periods. All that 

 we can see, and feel, and infer, and reason about may 

 be, as it were, but a part of one single pulsation in the 

 existence of the universe. 



After Sir W. Thomson had pointed out the prepon 

 derating tendency which now seems to exist towards the 

 conversion of all energy into heat-energy, and its equal 

 diffusion by radiation throughout space, the late Pro 

 fessor Rankine put forth a remarkable speculation k . He 

 suggested that the ethereal, or rather, as I have called it, 

 the adamantine medium in which all the stars exist, and 

 all radiation takes place, may have bounds, beyond which 

 only empty space may exist. All heat undulations reach 

 ing this boundary will be totally reflected, according to the 

 theory of undulations, and will in all probability be recon- 

 centrated into foci situated in many parts of the medium. 

 Whenever a cold and extinct star happens to pass through 

 one of these foci, it will be instantly ignited and resolved 

 by intense heat into its constituent elements. A discon 

 tinuity will occur in the history of that portion of matter, 

 and the star will begin its history afresh with a renewed 

 store of energy. 



This is doubtless a mere speculation, incapable of veri- 



k Report of the British Association (1852), Report of Sections, p. 12. 



