30 



THE PHILOSOPHY OF BIOLOGY 



motions of the earth, sun, and moon must retard the 

 period of rotation of the earth so that the intervals 

 between two successive transits of a star must become 

 greater. 



Thus we do not conceptuahse the actual intervals 

 of duration of which we are able to mark the end- 

 points ; they are lived by us, and they are real absolute 

 things independent of our wills. Suppose we come in 

 from a long walk, tired and thirsty, and ask the maid 

 to get tea ready at once. She puts the kettle on the 

 gas stove and then sits down to read. The water takes, 

 say, five minutes to boil. What do we mean by this ? 



This is what we mean : — 



What we call time here is only a series of simul- 

 taneously occurring events. The standard events are 

 the positions of the hands of the clock on the clock 

 face, that is, lengths of arc recording the number of 

 swings of the pendulum that have occurred since the 

 beginning of the operation of the boiling of the kettle. 

 When this began, the hands of the clock were at, say, 

 4.30, and the temperature of the water was then, say, 

 17° C. ; and, when it ended, the hands of the clock were 

 at 4.35 and the temperature of the water was 100° C. 

 It is only the simultaneities of these events that we 

 have recorded and not the interval of duration that 

 they mark. It does not matter how many times we 



