24 WILLIAM M. HAMLET. 



is resolved a stage further in the direction of simplification to 

 methane, which with hydrogen and carbon dioxide, are the 

 principal gases evolved in the process. After the discovery of the 

 function of nitrification brought about by the nitrifying organisms 

 by Warrington and Percy Frankland, the State Board of Health 

 of Massachusetts in 1888-9 were induced to try the method of 

 natural self-purification by these organisms. To Captain Sir 

 Douglas Galton 1 belongs the credit of introducing the system to 

 the notice of English sanitarians. The process was very soon 

 tried, and Dibdin in 1893, was astonished to find that by merely 

 passing sewage through a shallow coke filter, he obtained a fairly 

 good effluent, as good as some that were then being obtained by 

 more expensive precipitation processes. 



Scott-Moncrieff in 1892 devised a clever application of the 

 system, using an open tank filled with flints for the first 

 fermentation, then passing the liquid over a series of trays con- 

 taining coke, all exposed to the air, whereby the work of the 

 nitrifying organisms had full effect, resulting in a beautiful clear 

 effluent approaching in character to a potable water. Donald 

 Cameron was the first to boldly take the process in hand and use 

 it on a large scale, which he did in 1896 at Belle Isle, Exeter, 

 since when, it has been known as the Biological Method, or 

 Septic Tank System. 



It should here be stated that several modifications have been 

 introduced by others, so that we have the primary biological 

 method, with or without previous chemical precipitation processes, 

 but the true zymolysis of sewage should be carried on with absolutely 

 no addition of chemicals or antiseptics whatsoever. 



Ducat introduced his aerated, bacterial, self-acting coke-bed in 

 1897; Dibden 2 had, however, been working at the natural or self- 

 purification of sewage from 1884 to 1898, and his results, obtained 

 by simply passing crude sewage through coke and 'breeze' filter- 



1 Jour. Sanitary Institute, Vol. xvn. p. 1. 



2 Journ. Soc. Chem., Ind., Vol. xiv., p. 922; and Idem, Vol. xvn., p. 315* 



