26 jNTew York State 



age are similarly transformed under favorable conditions in a 

 stream and have been used in sewage forms for the enrichment of 

 the soil with entire success from the biological standpoint, although 

 Jhe financial returns have not been satisfactory. The rapidity with 

 which these wastes in a stream are made into serviceable form for 

 the support of life has suggested their utilization in fish culture. 

 M. C. Marsh, formerly with the U. S. Bureau of Fisheries, has 

 described (1916) a plan in successful operation at Strassburg for 

 sewage disposal by fish culture. The sewage properly handled is 

 made over rapidly into food for plants and small animals, which in 

 turn serve as sustenance for small fish of various types. According 

 to Marsh, the series of ponds and the dispoal plant present a sightly 

 appearance, do not involve a nuisance and resemble any well-con- 

 ducted fish culture station. As the process is delicately balanced, 

 its successful and continuous operation depends on foresight and 

 constant expert care. It clearly illustrates the process of nature in 

 converting organic wastes into food materials and their appropria- 

 tion by new living organisms. 



This process, even to the item of its relation to fish culture, is 

 being carried on wherever domestic sewage is emptied into a stream. 

 In reporting biological investigation on the Illinois river, with 

 especial reference to " the enormous outpouring of Chicago sewage 

 into the upper Illinois " by the drainage canal, Forbes (1910) sums 

 up one aspect of the work in this statement : " The organic wastes 

 thus emptied into the stream are laid hold of by bacteria and proto- 

 zoa and passed up by successive steps to form the flesh and bone of 

 fishes, and thus finally those of men. The same may be said of the 

 organic wastes of the towns along the banks of the stream." 



As the quantity of waste materials added becomes larger, the 

 point is reached when it exceeds the amount that can be handled 

 promptly by the stream. This amount depends on several factors, 

 viz., the volume of the stream, the rate of flow, and the character of 

 shore ^nd bottom. These are features which determine the quantity 

 of dissolved oxygen in the water and its replenishment when 

 exhausted. They determine also the amount and development of 

 the " pollution carpet," as it is called above, and the other organisms 

 concerned in the process. When the stream is deep and flows 

 slowly between steep banks there is little opportunity to take up 

 oxygen and the processes of change proceed very slowly ; the con- 

 taminated area spreads down stream, and gradually transforms the 

 stream into a sewage d'tch or septic tank. This extension of the 



