The Domain of Physical Science 205 



They are certain analytical expressions containing various com- 

 binations of the potentials. What are the " potentials " ? Why, 

 that is just what I have been explaining to you ! 



The definitions of physics proceed according to the method 

 immortalised in " The House that Jack Built " : This is the 

 potential^ that was derived from the interval, that was measured by 

 the scale, that was made from the matter, that embodied the mass. . . . 

 But instead of arriving ultimately at " Jack," whom, of course, 

 everybody knows without need for an introduction, we make a 

 circuit back to the beginning of the rhyme ..." that killed the 

 rat, that ate the malt, that lay in the house — that was built by the 

 priest all shaven and shorn, that married , . ." So now we can 

 go round and round for ever. 



But perhaps the reader has already interrupted my explanation 

 of the law of gravitation. When the term " matter " was reached, 

 he cut it short. " You need not trouble to explain any more ; 

 you have at last got down to words I understand ; I happen to 

 know what matter is." Very good ; matter then is something 

 that Mr. X knows. It seems all right — " . . . that came from 

 the interval, that was measurejd by the scale, that was made from 

 the matter, that Mr. X knows." Next question. What is Mr. X ? 



The diagram here inserted will perhaps help to keep in mind 

 the essentials of our discussion — 



^ Potential 



Mass, Momentum, Interval 



and Stress ^ / 



\ / 



Matter-* — Clock and Scale 



/ 



Mr. X "^ 



?^ 



Undoubtedly it is of great importance that there exists this channel 

 leading to Mr. X — and beyond. It is, perhaps, not so simple a 

 channel as Mr. X at first supposed. He " knows " the matter of 

 the scale, but not by a feeler put out from his mind into the scale 

 existing in the external world. Certain radiations proceed from 



