CH. XXXI. ASTRONOMY. 287 



CHAPTER XXXT. 



SCIENCE OF THE NINETEENTH CENTURY. 



Difficulties of Contemporary History — Discovery of Asteroids or 

 Minor Planets between Mars and Jupiter — Dr. Olbers suggests they 

 may be fragments of a larger Planet — Encke's Comet, and the cor- 

 rection of the size of Jupiter and Mercury — Biela's Comet noticed 

 in 1826 — It divides into two Comets in 1845 — Irregular movements 

 of Uranus —Adams and Leverrier calculate the position of an un- 

 known Planet — Neptune found by these calculations in 1846 — A 

 Survey of the whole Heavens made by Sir John Herschel— His 

 work in Astronomy — Comets and Meteor- systems. 



We have now arrived fairly at the beginning of our own 

 century, and shall have to speak of events which happened 

 as it were but yesterday, and of men whom our grandfathers, 

 or even perhaps our fathers, have seen and known. How 

 are we to find our way through the mass of discoveries 

 which have been made in every science during the last 

 seventy years, or to make our choice among the number of 

 famous men whose names we meet with every day ? We 

 must begin at once by recognising that it is impossible to 

 mention all, even of the leading points, of the science of our 

 time, and then we may try to learn a few of them, if we do 

 so with a clear understanding that we are leaving important 

 gaps unfilled. 



There are two special difficulties which we must en- 

 counter in the history of this century; first, we cannot 

 avoid mentioning the work of some living men, while at the 



