liv REPORT — 1853. 



fore altered, in a degree altogether inconsistent with the theory of non-pro- 

 gression. 



Mr. Rankine, however, has ingeniously suggested* aw hypothesis according 

 to which the reconceiitration ol' heat is conceivable. Assuming the physical 

 universe to be of rinite extent and surrounded by an ahsolute vacuum, radiant 

 heat (supposing it to be propagated in the same way as light) would be in- 

 capable of passing into the vacuum, and would be reflected back to foci cor- 

 responding to the points from whicli it emanated. A reconcentration of heat 

 would thus be effected, and any of tlie heavenly bodies which had previously 

 lost their heat, might, on passing through these foci, be rekindled into bright 

 centres of radiant heat. 1 have alluded more particularly to tiiis very inge- 

 nious, tliougli, perhaps, fanciful hypothesis, because some persons have, I 

 believe, regarded this view of the subject as affording a sanction to the 

 theory of non-progression ; but even if we should admit its truth to the 

 fullest extent, it may be deemed, I think, entirely inconsistent with that uni- 

 formity and permanence of physical condition in any of the heavenly bodies 

 which the theory just mentioned requires in our own planet. The author of 

 this hypothesis did not possibly contemplate any such application of it ; nor 

 am I aware how far he would advocate it as really applicable to the actual 

 constitution of the material universe, or would regard it as suggesting a pos- 

 sible and conceivable, rather than a probable, mode of counteracting the 

 constant dispersion of heat from its existing centres. He has not, I think, 

 attempted to work out the consequences of the hypothesis as applied to light, 

 to which it must, I conceive, be necessarily considered applicable if it be so 

 to heat. In such case the foci of the reflected heat would be coincident 

 with those of the reflected light, proceeding originally from the same lu- 

 minous bodies. These foci would thus become visible as the images of stars ; 

 so that the apparent number of stars would be constantly increasing with the 

 increasing number of images of each star produced by successive reflexions. 

 This will scarcely be considered the actual order of nature. It would be 

 easy to trace other consequences of the application of this hypothesis to 

 light ; but I would at present merely state that my own convictions entirely 

 coincide with those ol' Prof. Thomson. If we are to found our theories 

 upon our knowledge, and not upon our ignorance of physical causes and 

 phasnomena, I can only recognise in the existing state of things a })assing 

 phase of the material universe. It may be calculated in all, and is demon- 

 strably so in some respects, to endure under the action of known causes, for an 

 almost inconceivable period of time; but it has not, I think, received the im- 

 press of eternal duration, in characters which man is able to decipher. The 

 external temperature and physical conditions of our own globe may not, and 

 probably cannot have changed in any considerable degree since the first 

 introduction of organic beings on its surface ; but I can still only recognise 

 in its physical state, during all geological periods, a state of actual though of 

 exceedingly slow progression from an antecedent to some ultimate state, on 

 the nature of which our limited powers will not enable us to offer any con- 

 jecture founded on physical research. The theories, even, of which I have 

 been speaking, may probably appear to some persons as not devoid of pre- 

 sumption; but for many men they will ever be fraught with deep speculative 

 interest; and, let me add, no charge of presumption can justly lie against 

 them, if entered upon with that caution and modesty which ought to guide 

 our inquiries in these remote regions of physical science. 



I feel how imperfect a view I have now submitted to you of recent scien- 

 tific proceedings. I have given no account of the progress of Chemistry, 



