252 POINTER READINGS 



problem and an angle of 6o° takes its place. What is 

 6o°? There is no need to struggle with mystical con- 

 ceptions of direction; 6o° is the reading of a plumb-line 

 against the divisions of a protractor. Similarly for the 

 other data of the problem. The softly yielding turf on 

 which the elephant slid is replaced by a coefficient of 

 friction, which though perhaps not direcdy a pointer 

 reading is of kindred nature. No doubt there are more 

 roundabout ways used in practice for determining the 

 weights of elephants and the slopes of hills, but these 

 are justified because it is known that they give the same 

 results as direct pointer readings. 



And so we see that the poetry fades out of the prob- 

 lem, and by the time the serious application of exact 

 science begins we are left with only pointer readings. 

 If then only pointer readings or their equivalents are 

 put into the machine of scientific calculation, how can 

 we grind out anything but pointer readings? But that 

 is just what we do grind out. The question presumably 

 was to find the time of descent of the elephant, and the 

 answer is a pointer reading on the seconds' dial of our 

 watch. 



The triumph of exact science in the foregoing problem 

 consisted in establishing a numerical connection between 

 the pointer reading of the weighing-machine in one 

 experiment on the elephant and the pointer reading of 

 the watch in another experiment. And when we examine 

 critically other problems of physics we find that this is 

 typical. The whole subject-matter of exact science 

 consists of pointer readings and similar indications. 

 We cannot enter here into the definition of what are 

 to be classed as similar indications. The observation of 

 approximate coincidence of the pointer with a scale- 

 division can generally be extended to include the 



