CH. xxxi. SSK WILLIAM HERSCHEL. 281 



gravitation holds them all in one eternal round about their 

 sun. 



These are some of the problems solved by Lagrange and 

 Laplace. You cannot expect to understand their full signi- 

 ficance, nor must you imagine that these few pages contain 

 more than a very small fraction of the work which these 

 two mathematicians accomplished. Laplace made some 

 beautiful calculations explaining the theory of the tides, and 

 you will also often hear him mentioned as the author of the 

 1 Nebular Hypothesis," by which he taught that our earth 

 and all the planets were in the beginning formed by the 

 condensation of gases and fluid matter. All this, which is 

 too difficult to enter upon here, is discussed in his famous 

 work, the * Me'canique Celeste,' published in 1799. But 

 the main points to be remembered are that Lagrange and 

 Laplace proved the regular order of the movements of the 

 planets, and explained all those anomalies which had seemed 

 to be out of harmony with Newton's theory of gravitation. 



Sir William Hersehel constructs his own Tele- 

 scopes, and discovers Uranus, 1781. William Her- 

 sehel, who was born in 1738, was one of ten children. 

 His father, who was an eminent musician, brought him up 

 to follow his own profession, and when William came over 

 to England with his regiment, he started in life as a teacher 

 of music. The first three years in this country were years 

 of hard struggle and privation, but at last he was appointed 

 organist at Halifax in Yorkshire, and from there he went in 

 1766 to Bath, where he soon became known as a talented 

 musician, playing in the Octagon Chapel and at concerts 

 and parties with immense success, and attracting a large 

 number of private pupils. 



1 This hypothesis had, however, been elaborated before the time of 

 Laplace by the celebrated philosopher Kant 



