1888.] MICROSCOPICAL JOUENAL. 91 



the germs of numerous forms of infusorial life, but that it contains the nu- 

 trient piunciple necessary to the development of such forms. 



Second. The considerable diversity of forms which are found indicates a 

 corresponding diversity in the quality of the nutrient principle. 



Third. The profusion of forms found in dead ends and in mains with in- 

 adequate circulation indicates that light is not essential to the development 

 of the lower forms of life. 



Fourth. The city water department has been aware for several years that 

 dead ends require frequent flushing, made manifest to the department by fre- 

 quent complaints from consumers as to the quality of the water at such points. 

 The results of our study may. therefore, stand as justification of the expense 

 of a systematic flushing of mains by that department. 



Fifth. The farther conclusion may be drawn not only by the management 

 of our own water-works, but by all engineers engaged in designing and con- 

 structing water-works, that thorough circulation is of prime importance, and 

 this work appears to furnish justification of considerable additional expendi- 

 ture in order to secure thorough circulation in every part of a pipe distribu- 

 tion system. 



Sixth. The question of covered versus open reservoirs has been considerably 

 discussed, not only by engineers, but by chemists and biologists, and widely 

 varying opinions have been expressed. The opinion has been generally held, 

 however, that covered reservoirs are necessary to prevent the development 

 of life in standing water, and in England large amounts have been expended 

 in constructing reservoirs with masonry covering. Our study of the develop- 

 ment of life in the mains appears to justify the opinion that at present the 

 utility of such expensive constructions is not fully proven. 



Concluding this part of the subject your attention is directed to the fact 

 that this work has therefore in addition to its purely scientific aspect a fair 

 proportion of commercial value. 



SANITARY CONSIDERATIONS. 



The question will at once arise. Are any of the forms now known to exist 

 in the water of Hemlock lake such as really indicate organic impurity, and 

 are they farther such as are prejudicial to the public health ? A complete 

 answer to this question would involve tracing the life-history of each and 

 every form, and this cannot at present be done. We have, however, certain 

 known points established from which we may reason to definite conclusions. 

 For instance, certain algae are known to produce diarrhoeal difiiculties, and an 

 excessive amount of certain algae present in a public water supply has been 

 accompanied by an alarming mortality of the fish. Several water supplies 

 have been at times very oflensive by reason of the presence of a large amount 

 of sulphureted hydrogen caused by the decomposition of algte. Again, 

 the presence of nematoid worms and small leeches may give rise to certain 

 grave disorders of the human system which we cannot go into here. There 

 are, however, numerous forms, both animal and vegetable, to which no 

 special effect on health can, at present, be assigned. In any case a knowl- 

 edge of their existence is important as indicating the presence of organic im- 

 purities or as possibly indicating putrefaction, and even though we have as 

 yet no evidence that they are harmful, still we would not hesitate to condemn 

 a water found swarming with any of the lower forms of life. 



In thus presenting the present sanitary condition of the water of Hemlock 

 lake, thei'e is no intention of alarming either the members of the Academy or 

 the public. Indeed, we do not consider the contamination as yet great 

 enough to be the cause of any serious alarm. We do think, however, that 

 the gradually increasing contamination which has been shown to exist is a 



