138 MORE POT-POURRI 



ing the last few days one cannot realise it is the week, 

 not of the shortest days, but of the shortest afternoons 

 of the whole year. This sentence brought about a 

 fearful coolness between me and my dear secretary, 

 who asked for an explanation of the statement, and, 

 when I tried to give it, failed to understand. We agreed 

 to refer the matter to an authority that we both believed 

 in. The next day brought the following reply • ' The 

 explanation you require is, I think, hardly suited to 

 "Poi-PoMrn." I should put it somehow thus, "that 

 week in which the almanack tells us the days are grow- 

 ing shorter, though the sun sets at a later hour." Of 

 course the afternoon does not grow longer. Noon is the 

 moment at which the sun crosses the meridian, and it 

 then attains its highest point for the day ; and, of 

 course, if it rises later, it also sets earlier. The appa- 

 rent anomaly occurs thus — the solar day, which is 

 measured from the time the sun crosses the meridian 

 on one day to the time it does ditto on the next, is not 

 of uniform length. The reasons — which you need not 

 read — are : (1) The path of the sun does not lie in the 

 equator, but in the ecliptic ; (2) owing to the earth's 

 orbit not being circular, its motion in the ecliptic is not 

 uniform. Now, it would manifestly be very uncom- 

 fortable to have days of varying length ; therefore, an 

 imaginary sun has been invented which is supposed to 

 behave in a decent and orderly fashion ; the time by 

 him is called "mean time," and is that shown by a 

 watch. The time shown by the real sun is called 

 "apparent time," and is that shown by a sun-dial. 

 The difference between these two times is as much as 

 sixteen minutes at certain seasons of the year. Now, 

 on the shortest day the sun crosses the meridian nearly 

 two minutes before twelve o'clock. He was earlier 

 the few days before ; therefore, his time of setting 



