32 GEORGE W. FULLER 



mentally as has been the case with sewage-works. In earlier years 

 however, experimental methods had much to do with the develop- 

 ment of water filters abroad. It is not to be forgotten, furthermore, 

 that in Germany much good work during the past dozen years has 

 been done in developing the most practical methods for removing 

 iron from ground waters. At present the most interesting feature 

 of water-purification developments in Europe refers to the prelimi- 

 nary treatment for some of the river waters which are fairly turbid 

 during freshets, and to efforts to sterilize water economically by 

 ozone. The most notable instance of the former is at Suresnes, 

 near Paris, where the Seine water below the metropolis is subjected 

 to filtration six times, the first filters being of coarse gravel to effect 

 clarification. 



In England, which is the home of modern sanitary engineering, 

 sewage-purification works have received more attention than in 

 any other country. The density of population in England and 

 the relatively small size of its rivers have, of course, forced this con- 

 dition at an earlier date than is generally true of other countries. 

 While for some years the English have not contributed much on 

 the subject of water filtration, their experience in the field of sewage 

 purification far exceeds that of any other country. Experimental 

 methods in one form or another have played an important part 

 for half a century, beginning with efforts to utilize the manurial 

 value of sewage. This is largely owing to the differences in various 

 local conditions, especially topography, geology, and the compo- 

 sition of the sewage as influenced by trade wastes. Not only have 

 the English conducted test filters and other processes of purification 

 on a small scale, but they have also gathered many data of great 

 value by the operation of their works in practice along lines which 

 enable current experiences to be utilized in developing future works. 



These data have been so universally obtained in conjunction 

 with the operation of existing works in practice that it is very difficult 

 to ascertain even roughly what their cost has been. The staff regu- 

 larly engaged in operating the main works has secured the technical 

 data, so that the expense has been confined to building the test 

 devices, relatively small in size, and to a little extra labor for opera- 

 tion. The large mass of valuable testimony published in numerous 



