244 THOUGHTS ON THE NATURE AND ORIGIN OF FORCE. 



These consideratious, of course, apply equally to all tlie various kinds 

 of molecular movemeut, such as those of light, of heat, and of electrical 

 currents. It is familiar to all that we can create heat, as when we kin- 

 dle a lire in the stove, or pass an electrical current through an imper- 

 fect conductor, or simply rub two sticks together. It is equally familiar 

 that v.'e can destroy heat, as when we employ steam-power for welding, 

 forging, rolling, or swaging iron, and measure the effective work per-| 

 formed in these operations by the amount of heat abstracted from the 

 steam, and forever destroyed as heat. In brief, whenever heat or other 

 movement has produced a changed effect in matter, either internally or 

 externally, there and to that precise extent has the motion (whether 

 molar or molecular) entirely disappeared. 



It is true that we still hear the convenient term '''■latent heat" fre- 

 quently employed ; but while holding in all honor the researches of Black, 

 who first unfolded to us the curious phenomena grouped under this title, 

 we now know by tlie clear light of the dynamic theory that there is no 

 such thing as latent heat; that if heat be not sensible, or actual, it is not 

 heat at all. We now know that the 142° necessary to liquefy melting 

 ice without any increase of temperature, and the 9G5^ absorbed in effect- 

 ing the evaporation of boiling water, have had to overcome great mole- 

 cular resistances ; and that the internal work thus performed in raising 

 the water to a higher potential is exactly measured by the amounts of 

 heat respectively thus expended and consumed. When, true to tke 

 eternal law of conservation, precisely similar amounts of heat are ob- 

 tained by a reversal of the several processes, these temperatures are as 

 much a new creation or transformation as when we ignite the carbu- 

 reted hydrogen at our gas-burners, or the anthracite in our grates. 



No one would think of saying (excepting metaphorically) that we 

 were releasing tlie light and heat stored up — in the one case at the 

 retorts of the gas-factory, and in tlie other in the carboniferous labora- 

 tory of the solar actinism — a million years ago. Heat latent in coal-, 

 fields which may perchance have lain immediately beneath colossal 

 glaciers for thousands of years ! As well might we si^eak of the blaze 

 emitted by the petroleum lamp as original sun-light which has been 

 latent all these millenniums. 



Undoubtedly the more accurate designation of the fact is, that when 

 motion has resulted in static condition, the motion is absolutely de- 

 stroyed ; when from that condition a succeeding motion is evolved, a 

 new motion has been as absolutel}" created; that when one kind of 

 motion has been transformed into another kind of motion, the equivalence 

 of the two by no means involves the identity of the two. 



Among the multitudinous metamorphoses of force presented to our 

 observation, Ave find not unfrequent examples of motion rising higher 

 than its source. These oases may, however, all be likened to the famil- 

 iar illustration of a large weight on the short end of a lever lifting a 

 lighter weight on the other end as many times as high ; or to the par- 



