vi PREFACE. 



of life and its conditions, are totally unknown to the 

 majority of otherwise well-educated persons. 



Great efforts are now being made to meet this 

 difficulty, by teaching children a few elementary facts 

 of the various branches of science ; but, though such 

 instruction is of immense value, something more is 

 required in order that the mind may be prepared to 

 follow intelligently the great movement of modern 

 thought. The leading principles of science ought 

 in some measure to be understood ; and these will, 

 I believe, be most easily and effectually taught by 

 showing the steps by which each science has attained 

 its present importance. 



It is this task which I have endeavoured to ac- 

 complish; and if teachers will make their pupils master 

 the explanations given in these pages and, wherever 

 it is possible, try the experiments suggested, I venture 

 to hope that this little work may supply that modest 

 amount of scientific information which everyone 

 ought to possess, while, at the same time, it will form 

 a useful groundwork for those who wish afterwards to 

 study any special branch of science. 



The plan adopted has been to speak of discoveries 

 in their historical order, and to endeavour to give such 

 a description of each as can be understood by any 

 person of ordinary intelligence. This has made it 

 necessary to select among subjects of equal impor- 

 tance those which could be dealt with in plain lan- 

 guage, and to avoid passing allusions to such as did 

 not admit of such explanation. 



