284 Dr. 0. J. Lodge on a Systematic Classification 



are competent to receive it. Hence energy possessed by them 

 is generally of a high form. 



17. Planetary masses can be dealt with singly indeed, but 

 so singly that there is scarcely* any other body accessible to 

 which their motion can be transferred! (see §§4 and 14). 



18. The energy of moving molecules is not very available 

 to us, because we can only deal with them statistically and 

 not individually. There is a large amount of relative motion 

 and transference of energy constantly going on among indi- 

 vidual molecules : but, as we have no control over it, the work 

 done is useless, and the energy unavailable. The only part of 

 the energy which can be transferred at will to external bodies 

 is that due to the average state of the moving molecules : and 

 it is not possible to transfer even this unless some other mass 

 is accessible, the average state of whose molecules in respect of 

 motion or strain is in some way different, so that the one is 

 able to do work upon the other J. 



Now since all accessible bodies have very large stores of 

 molecular energy, it follows that a very great portion of the 

 energy which belongs to the molecules of a body must be 

 totally unavailable to us, because it can never be got rid of or 

 transferred. And even the portion which can be transferred 

 at pleasure to some larger body, if not made use of quickly, 

 will be found to transfer itself to neighbouring molecules and 

 in directions not required, and will waste itself in doing use- 

 less work. Hence molecular energy is called a low form. 



19. Atomic or chemical energy seems at present to rank 

 a little higher than molecular energy ; for though one way of 

 availing ourselves of it is by converting it into molecular 

 energy (heat) and then doing useful work with the balance of 

 the average effect by which the body heated excels its neigh- 

 bours, yet animals and galvanic batteries are able to do useful 

 work with it in a more direct and less wasteful fashion. 



*<The well-known exception is the ocean, which by the agency of the 

 moon is put into a slightly different state of motion from the rest of the 

 earth ; and a minute portion of the earth's energy of rotation is constantly 

 being transferred to it. A portion of this tidal energy is now available to 

 us, and may be made to do useful work. 



t Hence the kinetic energy of the earth is of no more use to us than a 

 bank-note to Robinson Crusoe. 



X An analogy may be drawn between the molecular energy of a body 

 and the money of a bank ; of which a reserve fund is kept for internal 

 transfer and transactions between customers, while the excess gets invested 

 in external concerns which have a deficiency, and so becomes available 

 for doing useful work. To make the analogy more complete, the clerks 

 should be uniformly dishonest, or the coffers insecure, so that stored 

 money should dribble away. 



