INTRODUCTION. 



changes which take place when two substances act upon one 

 another so as to make a new substance. 



There are many simple books written now to explain 

 these sciences, and those who wish can read these books and 

 study the examples and experiments given in them. They 

 tell us what science now ts, and the explanations given by 

 the best men about the universe in which we live. But they 

 do not tell us how science has become what it is, and it is this 

 which I hope to tell you in the present book. 



A man who wishes to understand a steam-engine can do 

 so by going to an engineer and having each part explained 

 to him ; but if he wishes to know the history of the steam- 

 engine he must go back to the first one ever made, and 

 study each new improvement as it arose. And so if we go 

 back to the first attempts made by thoughtful men to under- 

 stand nature, and then trace up step by step the knowledge 

 gained from century to century, we shall have at least a more 

 intelligent understanding of that which is taught us now. 

 But if we have any true love of knowledge we shall gain far 

 more than this ; for in studying the history of those grand 

 and patient men who often spent their lives and made great 

 sacrifices to understand the works of God, the merest child 

 must feel how noble it is to long and strive after truth. 



When we go back to very early ages we do not find that 

 people understood much of what we now call science. So 

 long as men were chiefly occupied in protecting themselves 

 against other savage men and wild beasts, and had to 

 struggle very hard to get food and clothing, they had very 

 little time or wish to study nature. Still they learnt many 

 things which were necessary for their life. They learnt, for 

 instance, at what times the sun rose and set, for upon this 



