PREFACE. 



IT is very necessary that all who desire to become 

 really proficient in any department of science should 

 follow the beaten track, toiling more or less pain- 

 fully over the difficult parts of the high road which 

 is their only trustworthy approach to the learning 

 they desire to attain. But there are many who 

 wish to learn about scientific discoveries without this 

 special labour, for which some have, perhaps, little 

 taste, while many have scant leisure. My purpose 

 in the present work, as in my " Light Science for 

 Leisure Hours," the " Myths and Marvels of As- 

 tronomy," the " Borderland of Science," and " Science 

 Byways," has been to provide paths of easy access 

 to the knowledge of some of the more interesting 

 discoveries, researches, or inquiries of the science of 

 the day. I wish it to be distinctly understood that 

 my purpose is to interest rather than to instruct, in 

 the strict sense of the word. But I may add that it 

 seems to me even more necessary to be cautious, and 

 accurate in such a work as the present than in 

 advanced treatises. For in a scientific work the 

 reasoning which accompanies the statements of fact 



