276 EIGHTEENTH CENTURY. PT. III. 



method of observing the transit of Venus, which is now 

 used at stations where Halley's method (see p. 155) cannot 

 be applied. Delisle's method consists in marking the time 

 of commencement of the transit in one part of the world 

 where it begins earliest, and at another station where it begins 

 latest ; instead of measuring, as Halley did, the duration or 

 length of time occupied by the whole transit as seen at each 

 place. Halley's method requires the stations to be widely 

 apart, east and west, and Delisle's, north and south. 



These advances are all that need be mentioned during 

 the first half of the eighteenth century, but during that time 

 there had been born within a few years of each other three 

 men, Lagrange, Laplace, and Herschel, who were to light up 

 the close of the century with the most brilliant discoveries. 

 The two first of these were Frenchmen, the last, though a 

 German by birth, may almost be considered English as far as 

 science is concerned ; for though he was born at Hanover in 

 1738, of German parents, still Sir William Herschel came 

 over to England at the age of twenty-one, and all his dis- 

 coveries were made here. It was our King George III. 

 who gave him the pension which enabled him to devote 

 himself to science, and he made England his home and 

 country. His son, Sir John Herschel, who, like his father, 

 was one of our greatest astronomers, was born in this 

 country. 



Lagrange and Laplace. Louis de Lagrange was born 

 at Turin in 1736. His father, who had been Treasurer of 

 War, lost all his fortune when his son was quite a child, and 

 I^agrange often said that it was partly owing to this mischance 

 that he became a mathematician. His talent showed itself 

 so early that before he was twenty he was appointed 

 Professor of Mathematics in the Military College of Turin, 

 where nearly all his pupils were older than himself From 



