PREFACE TO THE FIRST EDITION 



The rapid development in modern ideas of sewage purification 

 by bacterial processes necessitates a careful review of the 

 methods of disposal at present sanctioned. The important 

 reports published by the London County Council, Manchester, 

 Leeds, and other towns in this country, as well as those of 

 commissions appointed by sanitary authorities in the United 

 States and on the Continent, and the frequent discussions and 

 papers in the technical press, lead me to the view that a resume 

 would be acceptable to a wide class of readers in this country. 



The Royal Commission at present engaged on this subject 

 will, no doubt, carefully weigh the evidence which is being 

 placed before it, and we may confidently expect that its conclu- 

 sions will be in accord with those obtained from the experiments 

 which have now been carried out on sufficiently large a scale to 

 establish the safety of embarking on the treatment of sewage on 

 bacterial lines for even the largest centres of population. 



The theoretical basis of the bacterial changes, so far as they 

 have been at present studied, must underlie all the practical 

 schemes which may in the future be put forward, and it has 

 been my endeavour in the following pages to deal with the 

 subject from this point of view. 



I have to thank many friends and firms for information and 

 the loan of blocks, and also my assistant, Mr. C. G. Sfewart, for 

 helping me in preparing the work for the press. 



Samuel Rideal. 

 28, Victoria Street, Westminster, 

 May, 1900. 



