136 POPULAR LECTURES AND ADDRESSES. 



globes were still taught, even to poor children, as 

 a pleasant and profitable sequel to " reading, writ- 

 ing, and arithmetic," which of us did not revere the 

 great telescope of Sir William Herschel (one of 

 the Hundred Wonders of the World), and learn 

 with delight, directly or indirectly from the charm- 

 ing pages of Sir John Herschel's book, about the 

 sun and his spots, and the fiery tornadoes sweeping 

 over his surface, and about the planets, and Jupiter's 

 belts, and Saturn's rings, and the fixed stars with 

 their proper motions, and the double stars, and 

 coloured stars, and the nebulae discovered by the 

 great telescope ? Of Sir John Herschel it may 

 indeed be said, nil tetigit quod non oniavit. 



With regard to Sir John Herschel's scientific 

 work, on the present occasion I can but refer 

 briefly to a few points which seem to me salient in 

 his physical and mathematical writings. First, I 

 remark that he has put forward, most instructively 

 and profitably to his readers, the general theory of 

 periodicity in dynamics, and has urged the practical 

 utilising of it, especially in meteorology, by the 

 harmonic analysis. It is purely by an application 



