PREFACE. ix 



that I have suggested in simple language the 

 right way to go to work. 



I must make an apology for the form in 

 which the essays are cast, so far as regards 

 the apparent egotism of the first person. 

 When they appeared anonymously in the 

 columns of a daily paper, this air of person- 

 ality was not so obtrusive : now that they 

 reappear under my own name, I fear it may 

 prove somewhat too marked. Nevertheless, 

 to cut out the personal pronoun would be to 

 destroy the whole machinery of the work : so 

 I have reluctantly decided to retain it, only 

 begging the reader to bear in mind that the 

 / of the essays is not a real personage, but 

 the singular number of the editorial we. 



I have made a few alterations and cor- 

 rections in some of the papers, so as to bring 

 the statements into closer accordance with 

 scientific accuracy. At the same time, I 

 should like to add that I have intentionally 



a 



