1882.] 4d< [Chase. 



that heat is radiated with infinite velocitj', inasmuch as Ihey take no ac- 

 count of the states of rehxtive rest or motion of the bodies between 

 which the heat passes. He cites the statement of KirchhofF, "that the second 

 law cannot be (at present) proved ; but it, so far, has never been found in 

 disagreement "witli experience;" the view of Maxwell and Boltzmann ( Wien 

 Sitzb., Biinde, Ixxvi, Ixxviii), that it should be regarded "as merely the 

 mean result flowing from the laws of probability ;" Rankine's paper {Phil., 

 Mag, [4] iv, 358), in which "he has supposed it possible to reflect radia- 

 tions in such a way as to give the universe such differences of temperature 

 as to insure it a new lease of life ;" and the paper of Clausius (Mech. Theory 

 of Heat, chap, xii), showing the general impossibility of such a reconcen- 

 tration as Rankine supposed, when the radiating bodies are at rest ; never- 

 theless, no such impossibility may finally appear in case of the actual uni- 

 verse which is a system ot moving bodies." He closes his discussion with 

 the following sentences: "The point to which I would emphatically 

 direct attention is, that since radiations are known to be moving in space, 

 apart from ponderable bodies, and subject to reflections, it is possible so to 

 deal with them as to completely alter their destination, and successfully inter- 

 fere with all results flowing from Prevost's law of exchanges. It also seems 

 to me that the exactness of the second law of thermodynamics depends, as 

 far as radiations are concerned, upon that of this law of exchanges." In 

 addition to the reflections to which moving radiations are subject, I have 

 also called attention to their refraction (Note 286), and I have endeavored 

 to co-ordinate all my discussions, through the fundamental identity (Note 

 280), which implies an equivalent motion of reaction for everj-- radiant 

 action. Moreover, the moving particles in each radiant undulation are all 

 subject to cosmical attractions and perturbations, which have not yet been 

 considered in investigations of the seeming dissipation of energy. 

 301. Thrust of Polar Ice- Caps. 

 Geologists whobelieve that the northern hemisphere was once largely cov- 

 ered with ice, have usually attributed the thrust to the smiple gravitating 

 pressure of the accumulation at the pole. The position of many of the bould- 

 ers, and of the supposed terminal moraines, seems to indicate a greater pro- 

 pelling force than many investigators are willing to attribute to the com- 

 bined action of polar centripetal and equatorial centrifugal energy. Per- 

 haps the unwillingness may be removed by making proper allowance for 

 "the flow of solids," an element of the problem which does not seem 

 to have received any consideration beyond the simple plasticity and regela- 

 tion which have been studied in connection with the movements of ordi- 

 nary glaciers. The photodynamic hypothesis of an all-pervading and 

 universally active aether involves the requirement of perpetual tendencies 

 toward equilibrium, and the evidence of such tendencies which is given by 

 Earth's oblateness (Notes 246, 249) furnishes an adequate explanation 

 for many of the glacial phenomena which have hitherto seemed paradoxi- 

 cal. Bessel's estimate of the oblateness is slightly less than would result 



