Ixiv REPORT ISGD. 



wliieli consfitiites liglit is transmitted across the intorpknetary spaces by a 

 highly ehistic ether, theii, unless this motion is confiued to one direction, 

 unless there be no interference, imless there be uo viscosity, as it is now- 

 termed, in the mcdiiim, and consequently no friction, light must lose some- 

 thing in its progress from distant luminous bodies, that is to say, must lose 

 something as light ; for, as all reflecting minds arc now convinced that force 

 cannot be annihilated, the force is not lost, but its mode of action is changed. 

 If light, then, is lost as hght (and the observations of Stru-se seem to show this 

 to be so, that, in fact, a star maybe so far distant that it can never bo seen in 

 consequence of its luminous emissions becoming extinct), what becomes of the 

 transmitted force lost as light, but existing in some other form ? So with 

 heat : our sun, our earth, and planets are constantly radiating heat into 

 space, so in all probability arc the other suns, the stars, and their attendant 

 planets. AYhat becomes of the heat thus radiated into space ? If the uni- 

 verse have no limit, and it is difficult to conceive one, heat and light should 

 be everywhere uniform ; and yet more is given off than is received by each 

 cosmicai body, for otherwise night would be as light and as wann as day. 

 What becomes of the enormous force thus apparently non-recurrent in the 

 same form ? Does it return as palpable motion ? Does it move or contri- 

 bute to move suns and planets ? and can it be conceived as a force similar to 

 that which Newton speculated on as universally repulsive and capable of 

 being substituted for universal attraction ? We are in no position at present 

 to answer such questions as these; but I know of no problem in celestial 

 dynamics more deeply interesting than this, and we may be no further re- 

 moved fi'om its solution than the predecessors of Newton were from the 

 simple dynamical relation of matter to matter which that potent intellect 

 detected and demonstrated. 



Passing from extraterrestrial theories to the narrower field of molecular 

 physics, we find the doctrine of correlation of forces steadily making its way. 

 In the Bakerian Lecture for 186-3 Mr. Sor])y shows, not perliaps a direct 

 correlation of mechanical and chemical forces, but that when, either bjr solu- 

 tion or by chemical action, a cliange in volume of the resulting substance as 

 compared with that of its separate constituents is effected, the action of 

 pressure retards or promotes the cliange, according as the substance formed 

 Avould occupy a larger or a smaller space than that occupied liy its separate 

 constituents ; the application of these experiments to geological incjuiries as to 

 subterranean changes which may have taken jAnce under gi'eat pressure is 

 oindous, and we may expect to form compounds under artificial compression 

 Avhich cannot be found under normal pressure. 



In a practical point of view the power of converting one mode of force into 

 another is of the highest importance, and with reference to a subject which 

 at present, somewhat prematurely perhaps, occupies men's minds, viz. the 

 prospective exhaustion of our coal-fields, there is every encouragement de- 

 rivable from the knowledge that we can at will produce heat by the expendi- 

 ture of other forces ; but, more than that, we may probably be enabled 

 to absorb or store up as it were diffused energy — for instance, Berthelot has 

 found that the potential energy of formate of potash is miich greater than that 

 of its proximate constituents, caustic potash and carbonic oxide. This change 

 may take place spontaneously and at ordinary temperatures, and by such 

 change carbonic oxide becomes, so to speak, reinvested with the amount of 

 potential energy which its carbon possessed before uniting witli oxygen, or, 

 in other words, the cai-bonic oxide is raised as a force-possessor to the place of 

 carbon by the direct absorption or conversion of heat from surrounding matter. 



