PREFACE, 



The book herewith offered has grown out of a se- 

 ries of articles printed in the first volume of Science 

 News, erstwhile published in New York under the 

 editorial eye of the present writer. 



In the course of their expansion the author has not 

 felt himself bound by any hard and fast limits in the 

 treatment of his subject, in respect either to the mat- 

 ters discussed or the manner of discussion. Inter- 

 mixed with essential information, therefore, will be 

 found a plentiful salting of facts and considerations, 

 which, if not important for their novelty or practical 

 value, may prove suggestive or at least entertaining. 



(vii) 



