207 



SCIENTIFIC SIDE-LIGHTS 



Ends 

 Ener 



ergy 



fined, force is any agency that can cause a 

 motion, arrest a motion, or change the direc- 

 tion of a motion, while energy is motion or 

 the capacity to become motion, and this car- 

 ries with it the idea of work. ELISHA GRAY 

 Nature's Miracles, vol. ii, ch. 1, p. 1. (F. 

 H. & H., 1900.) 



1012. ENERGY DERIVED FROM SUN 



All Work Result of Heat. This great 

 principle [the conservation of energy] en- 

 ables us to realize the absolute interde- 

 pendence of all the forces of Nature. It 

 teaches us that there is no origination of 

 force upon the earth, but that all energy 

 either now comes to us from the sun, or was 

 originated in the sun before our earth sepa- 

 rated from it; and we are thus led to the 

 conclusion that all work, all motion, every 

 manifestation of power we see around us, 

 are alike the effects of heat or of other radi- 

 ant forces allied to it. WALLACE The Won- 

 derful Century, ch. vii, p. 53. (D. M. & Co., 

 1899.) 



1013. ENERGY, ELECTRICAL, BAT- 

 TERY A STORE OF Resemblance of Elec- 

 tricity to Fire Force Stored in Coal or Zinc 

 Production of Power Costs Destruction of 

 Material (as Such). Again, it may be said, 

 with perfect truth, that every voltaic bat- 

 tery is a store of electrical energy. In a 

 voltaic battery some metal is employed, gen- 

 erally zinc, which, when the battery is work- 

 ing, is acted on chemically by an acid. The 

 effect of this chemical action is that the 

 atoms of the metal combine with the oxygen 

 of the acid; and by the act of combination 

 an electric current is generated. ... In 

 the case of coal, we have carbon and hydro- 

 gen existing apart from oxygen, with a 

 chemical force tending to make them com- 

 bine, under suitable conditions. We set up 

 these conditions when we light a fire: the 

 chemical force then comes into action; the 

 carbon and hydrogen rush to meet the oxy- 

 gen; and in the clash of atoms heat is 

 developed. Similarly, in the voltaic battery, 

 we have zinc existing apart from oxygen, 

 with a chemical force tending to pull them 

 together. We bring this force into action 

 when we arrange the cells of our battery 

 and make the necessary connections; the 

 atoms of zinc and oxygen then clash to- 

 gether, and, by the energy of their collision, 

 an electric current is generated. Thus it is 

 clear that, exactly in the same sense in 

 which heat energy is said to be stored in a 

 lump of coal, it may also be said that elec- 

 trical energy is stored in the zinc plates of 

 a battery. It is worth observing, too, that 

 both cases furnish a striking illustration of 

 a universal law of Nature. We cannot use 

 our store of energy, and keep our store, at 

 the same time. We cannot get heat from 

 coal except by a process in which the coal 

 is burned, and ceases to exist as coal. And 

 so, too, we cannot get an electric current 

 from our zinc plates except by a process in 



which the zinc is gradually consumed, and 

 ceases to exist as zinc. MOLLOT The Stor- 

 ing of Electrical Energy, p. 48. (Hum., 

 1889.) 



1014. ENERGY, MANUFACTURE OF, 

 IMPOSSIBLE Fallacy of Perpetual Motion. 

 One result of the due apprehension of our 

 personal helplessness will be that we shall 

 no longer waste our time over the impossible 

 task of manufacturing energy for ourselves. 

 Our science will bring to an abrupt end the 

 long series of severe experiments in which 

 we have indulged in the hope of finding a 

 perpetual motion. And having decided upon 

 this once for all, our first step in seeking a 

 more satisfactory state of things must be to 

 find a new source of energy. Following Na- 

 ture, only one course is open to us. We 

 must refer to environment. The natural life 

 owes all to environment, so must the 

 spiritual. Now the environment of the 

 spiritual life is God. As Nature therefore 

 forms the complement of the natural life, 

 God is the complement of the spiritual. 

 DBUMMOND Natural Law in the Spiritual 

 World, essay 7, p. 244. (H. Al.) 



1015. ENERGY OF POSITION Wafer 



at High Level Able To Do Work Crossbow 

 Bent Watch Wound Up. Let us suppose 

 there are two mills, one with a large pond of 

 water near it and at a high level, while the 

 other has also a pond, but at a lower level 

 than itself. We need hardly ask which of 

 the two is likely to work clearly the one 

 with the pond at a low level can derive from 

 it no advantage whatever, while the other 

 may use the high-level pond, or head of 

 water, as this is sometimes called, to drive 

 its wheel and do its work. There is, thus, a 

 great deal of work to be got out of water 

 high up real substantial work, such as 

 grinding corn or thrashing it, or turning 

 wood or sawing it. On the other hand, there 

 is no work at all to be got from a pond of 

 water that is low down. [By virtue of the 

 force of gravity] a stone high up, or a head 

 of water, is in a position of advantage, and 

 has the power of doing work as it falls to a 

 lower level. But there are other forces be- 

 sides gravity, and, with respect to these, 

 bodies may be in a position of advantage 

 and be able to do work just as truly as the 

 stone, or the head of water, in the case be- 

 fore mentioned. 



Let us take, for instance, the force of 

 elasticity, and consider what happens in a 

 crossbow. When this is bent, the bolt is 

 evidently in a position of advantage with 

 regard to the elastic force of the bow; and, 

 when it is discharged, this energy of posi- 

 tion of the bolt is converted into energy of 

 motion, just as, when a stone on the top of 

 a house is allowed to fall, its energy of posi- 

 tion is converted into that of actual motion. 



In like manner a watch wound up is in a 

 position of advantage with respect to the 

 elastic force of the mainspring, and as the 



