viii Preface 



the more positive method of a textbook, or to have entered 

 into the more minute detail of a handbook. 



In the incidental treatment of the technology of the subject 

 we have endeavoured to maintain the scientific perspective 

 rather than to discuss the practical details of processes. 



The photo-micrographs included in the work are from the 

 expert handiwork of our friend Mr. J. CHRISTIE, F.R.M.S., of 

 72 Mark Lane, E.G., to whom we record our best thanks for 

 this interesting addition to the subject-matter. 



The book is printed upon a paper carefully selected as 

 composed of the ' normal ' celluloses, and to the exclusion of 

 the inferior ' celluloses ' ordinarily employed for the manufac- 

 ture of printing papers. Upon the reasons for this preference 

 we have something to say in the text (p. 305). 



We have to thank our friend Mr. J. C. CHORLEY for contri- 

 butions of experimental results, and for kind assistance in con- 

 nection with the proofs. 



4 NEW COURT, LINCOLN'S INN, LONDON, W.C 



