30 LIGHT SCIENCE FOR LEISURE HOURS. 



OUR CHIEF TIME-PIECE LOSING TIME. 



A DISTINGUISHED French astronomer, author of one of 

 the most fascinating works on popular astronomy that 

 has hitherto appeared, remarks that a man would be 

 looked upon as a maniac who should speak of the 

 influence of Jupiter's moons upon the cotton trade. 

 Yet, as he proceeds to show, there is an easily traced 

 connection between the ideas which appear at first sight 

 so incongruous. The link is found in the determination 

 of celestial longitude. 



Similarly, we should be disposed to wonder at an 

 astronomer who, regarding thoughtfully the stately 

 motion of the sidereal system, as exhibited on a mag- 

 nified, and, therefore, appreciable scale by a powerful 

 telescope, should speak of the connection between this 

 movement and the intrinsic worth of a sovereign. The 

 natural thought with most men would be that 'too 

 much learning ' had made the astronomer mad. Yet, 

 when we come to inquire closely into the question of 

 a sovereign's intrinsic value, we find ourselves led to 

 the diurnal motion of the stars, and that by no very 

 intricate path. For, What is a sovereign? A coin 

 containing so many grains of gold mixed with so many 

 grains of alloy. A grain, we know, is the weight of 

 such and such a volume of a certain standard sub- 

 stance that is, so many cubic inches, or parts of a 

 cubic inch, of that substance. But what is an inch ? 



