504 PRESENT FUNDAMENTAL CONCEPTIONS OF PHYSICS. 



moving energy. The sudden heating of a moving body when arrested 

 is fully explained by this. 



Where did the moving energy originate which was imparted to the 

 body when thrown upward ? If we ourselves threw up the weight then 

 the energy came from our muscular power, which again drew it from the 

 vital power, that is, from a combination of physical and chemical forces; 

 the latter were again taken from that great total of nature's energy 

 which exists in unalterable quantity; this would be the case with any 

 other force which had been instrumental in throwing up the stone. The 

 masses of water of the cataract had at some previous time T>een carried 

 aloft; this was done through the agency of the energy of heat, by which 

 the water was raised in the form of vapor, and the latter by cooling off 

 reached that spot in the form of rain, from which, after numerous trans- 

 migrations and changes of locality, it Anally precipitates itself into the 

 deep. These processes resemble very much the changes through which 

 material substances pass in their innumerable physical and chemical 

 actions. However great the differences, it is certain that no substance 

 is ever lost in the universe : the transformation is simply like the build- 

 ing of a new edifice with old building stone; in this process the old 

 energies also contribute, but in new forms. 



The conservation of energy has its analogue, its precursory, necessary, 

 and supplementary correlative in the conservation of matter. As mat- 

 ter without force and force without matter are inconceivable, the great 

 discovery of Lavoisier (1772-'80) of the indestructibility of matter in 

 reality involved that of the indestructibility of force; nevertheless, half 

 a century passed away before this was recognized. The conservation 

 of energy, an acquisition of the present, and the permanence of matter, 

 an acquisition of the last century, together form the fundamental law 

 and the "center of gravity" of our modern natural science. 



On reaching this point, it may be interesting to search in the annals 

 of science whether in earlier times the truth of the persistence of mat- 

 ter and energy had not been discovered and lost again, or whether its 

 high importance and bearings were not comprehended. Researches in 

 this direction result in finding that indeed the ancient Greek philoso- 

 phers (Leucippus, 510 IJ. 0., Democritus, 470 U. 0. ; Aristotle, 350 

 B. C, and others), and more than two thousand years later, thinkers 

 and investigators like Descartes, Newton, lluyghens. Bacon, and others, 

 had an idea of the indestructibility of the atoms of matter, of the perpet- 

 ual activity and motion of the same ; that the former at times had a dim 

 perception of the indestructibility of matter and energy, and the latter 

 passed closely by tins fundamental proposition; that however only 

 within the last quarter of the last century has the theory of the inde- 

 structibility of matter, and within our own time the theory of the inde- 

 structibility of energy, been fully apprehended, and efforts made to 

 prove the same by means of induction. 



Against these proofs the objection has been raised that the constancy of 



