64 SIXTEENTH CENTURY. PT. HI. 



that, though the Greeks had learned much about nature, yet 

 their greatest men had only made the best theories they 

 could from the facts they knew, and had never intended that 

 their teaching should be considered as complete or final. 



And so little by little real observations and experiments 

 began to take the place of mere book-learning, and as soon 

 as this happened science began to advance rapidly so 

 rapidly that from this time forward we can only pick out the 

 most remarkable among hundreds of men who have added 

 to the general stock of knowledge. A detailed account of all 

 the steps by which the different sciences progressed would 

 fill many large volumes, and would only confuse you, unless 

 you already knew a great deal about the subject In this 

 book we can only throw a rapid glance over the last four cen- 

 turies of modern science, and try to understand such new 

 discoveries as ought to be familiar to every educated person. 

 But you cannot bear in mind too often that when we come 

 to a great man who discovers or lays down new laws, there 

 have always been a number of less-known observers who 

 have collected the facts and ideas from which he has formed 

 his conclusions, although to mention all these men would 

 only fill your mind with a string of useless names. 



I must also explain here why I have adopted the plan 

 of giving new discoveries in the order in which they oc- 

 curred. You would no doubt have understood each separate 

 science better if the account of it had been carried on 

 without any break if, for example, Astronomy had been 

 spoken of first, then Optics, then Mechanics, and so on. 

 But by this arrangement you would not see the gradual way 

 in which our knowledge has grown from century to century, 

 nor how the work done in one science has often helped to 

 bring out new truths in another. Therefore, although by 



