OF ARTS AND SCIENCES. 175 



classed with putrid waters, there are periods every warm season dur- 

 ing which it closely approaches to these in characters. 



" In the latter part of October last, I was watching for the inci'eased 

 amount of organic acids due to the decomposition of vegetable matter 

 after a season of drought, succeeded by copious rains, when I was great- 

 ly surprised to find the humates and apocrenates giving placp to crenic 

 acid and crenates, accompanied by a perceptible odor of decomposing 

 vegeto-animal matter, such as is emitted by freshly disturbed soil. This 

 odor, which characterizes the humus from animal matter, continued 

 several days ; the water became colorless, while the organic matter, 

 including carbonic acid, increased so as to exceed nineteen times the 

 minimum amount previously found. 



" The condensed vapor from the water had a strong odor of earth, 

 or precisely that of guano from humid climates, and possessed an acid 

 reaction. No more than mere traces of ammonia could be thus de- 

 tected. When the water was mixed with lime and distilled, the 

 condensed vapor was ammoniacal ; proving that no carbonate of 

 ammonia from the soil was present, but a salt of ammonia ^ due to de- 

 composition. The earthy odor, or so-called taste, was succeeded by 

 one closely resembling that of fresh-water fish, which, with slight 

 variations of intensity, has continued nearly ten weeks. 



" Before the water throughout the city became thus contaminated, 

 the suggestion arose that the cause was local ; the secondary main pipe 

 supplying my dwelling having perhaps retained some decaying parts 

 of eels or fish. A careful examination of the water was made, and 

 by analysis a portion of oil was separated from water, which had been 

 filtered through muslin to remove suspended impurities. 



" By distillation the odor could be isolated from the water, which 

 thus lost what was pronounced by good judges to be the flavor of fish- 

 oil ; while the water retained the oil, almost destitute of odor. 



" The general supply of water to a populous city had thus become 

 very offensive, without any adequate cause appearing, and the evil led 

 to the expression of many hypotheses and suppositions, chiefly without 

 reliable support. As the subject was one which was within the reach 

 of experiment, the course adopted was the following. 



" A displacement apparatus of glass was charged with recently cal- 

 cined animal charcoal, of medium fineness ; over this was placed a coni- 

 cal filter of clean cotton, so that any water falling on the charcoal 

 would first pass through the cotton filter. The water from a contracted 

 supply pipe was allowed to flow slowly on the cotton filter, and passed 



