May 26, 1893.J 



SCIENCE. 



285 



greatly improve the condition of the water. Much of the water 

 from the upper Hudson and the northern tributaries of the Mo- 

 hawk shows the effect of this sort of pollution, but the dilution 

 from comparatively unpolluted sources is great enough to reduce 

 it far below the objectionable point. 



After this study, which usually is not very important, comes 

 the study of the pollution by the population on the watershed. 

 In investigating the purity of an established supply or in select- 

 ing a new one this is the most important study of all. We have 

 approached the subject in three ways, keeping the results ob- 

 tained by the three processes in juxtaposition so that they can be 

 used as mutually explanatory. The first and, after sufiBcient 

 experience in judging effects,- the best method is by actual in- 

 spection of the polluting matters discharged into the stream. 

 These matters consist of sewage, garbage, drainage from fertil- 

 ized fields and other sources of animal matter, and the discharges 

 from manufacturing establishments, some of which are chemi- 

 cals and some putrescible organic refuse. In connection with 

 this inspection goes a determination of the amount of water 

 flowing in the stream at the point of entrance of the polluting 

 matter A careful study of the relative amounts of polluted 

 liquid and river water with the proper consideration of the 

 amount of pollution the water already contains and the char- 

 acter of the new supply will give a very clear idea of the condi- 

 tion of the resulting mixture. Detailed study by chemical and 

 biological methods of typical conditions will bring one to the 

 ability to determine by the inspection the probable condition of 

 new streams in approximately the same circumstances. In our 

 own case, having but little material obtained under the condi- 

 tions existing in this country, it was necessary to make this de- 

 tailed examination. 



The second jjrooess applied to the river was, therefore, the 

 chemical analysis of numerous samples from various places. It 

 is usually considered that the elements determined in water 

 analysis which denote the amounts of organic matter in different 

 forms and the amount of salt are the important ones. The list 

 included, therefore, albuminoid and free ammonia, nitrogen as 

 nitrates and as nitrites, chlorine, oxygen absorbed, as well as the 

 total solids, loss on ignition, color, appearance, and odor at 

 100° F. 



The third process applied was the biological analysis of sam- 

 ples of water taken from the same places as those for chemical 

 analysis and from many more. The biological analysis may be 

 made with reference to the number and kinds of algae, infusoria, 

 and other microscopic animal and vegetable life, with reference 

 to the numbers of bacteria, and with reference to the numbers of 

 such species of bacteria as can be recognized as coming from 

 sources which are dangerous or suspicious. All of these deter- 

 minations will be valuable in deriving a basis for a definite 

 opinion as to the character of the water. A few experiments 

 were made under the first head, and it was found that as regards 

 flowing water in rivers this determination was not as necessary 

 as others, moreover, the methods of such analysis have been well 

 elaborated by others, therefore it was left until a more convenient 

 season. It is advisable to make this analysis on some samples, 

 however, to secure the fullest knowledge possible. 



As regards the determination of numbers of bacteria, it was 

 soon discovered that in order to deteruiine the relative amounts 

 of pollution in the rivers at different places, it is necessary to re- 

 duce the possible sources of addition to the numbers of bacteria 

 to a minimum. This is done by waiting until a rainless period, 

 or nearly so, has intervened of sufficient duration to reduce the 

 river to its low stage and then give time for the collection of the 

 samples. It is possible by taking this precaution to show the in- 

 crease in pollution by showing the increase in numbers of bac- 

 teria below the source of pollution. Rains, sharji and heavy or 

 long continued, will wash into the stream much matter from the 

 soil, abounding in bacteria, so that the indications of pollution 

 from the constant flow of sewers and the like will be gi-eatly ob- 

 scured. It is probable, also, that it would be difficult to compare 

 the purity of two streams in widely different parts of the country 

 or in different conditions as to soil, slopes, area of watershed, 

 etc., on account of the consequent variations in numbers from 



what may be called outside sources. Our work has shown the 

 possibility of determining the relative increase in pollution in the 

 flow of a single river when propet precautions are taken. One 

 point to be mentioned is that where sewage ia discharged into 

 still water much of it will settle at once and samples taken near 

 the surface will not show t le full effect of its presence. 



The numbers of bacteria, at least unless determined without 

 the greatest care to eliminate all disturbing conditions, are not 

 therefore so important an indication as is desired. It is well 

 known that there are species of bacteria which exist under their 

 most favorable conditions in the inte.^tines of men and the higher 

 animals, but will live for a greater or less length of time in other 

 places. If the numbers of such bacteria could be ascertained the 

 relative amount of pollution from such suspicious sources would 

 be best determined. On the recommendation of Dr. Theobald 

 Smith of Washington we tried the method of determining the 

 numbers of Bacillus coli communis, by the fermentation-tube 

 method. This bacillus was selected because it is the most com- 

 mon in fecal matter and its growth in such media as ordinary 

 river water at ordinary tetnperatui-es is believed to be very slow, 

 if there is any. The method suggested by Dr. Smith was found 

 to be easily applicable in practice, and some very valuable results 

 have been secured. It promises to be a most valuable aid in de- 

 termining the pollution of water, and is especially valuable 

 because it gives the statement of the serious part of the pollution, 

 while all the other metliods mentioned are open to the objection 

 that they may reject a water which has a large amount of pollu- 

 tion not from dangerous sources, the water being, therefore, 

 comparatively clean; while they may, on the other hand, pass as 

 good water which shows out little actual amount, that amount 

 being of a very suspicious nature. 



Many of the results of the investigation whose program me is pre- 

 sented above, are given in the last four reports (tenth to thir- 

 teenth) of the N. Y. State Board of Health. A paper by Dr. 

 Smith, giving the argument for the selection of B. coli communis 

 as the index of pollution, is given in the thirteenth report. The 

 investigation is not yet finished, and other reports will follow 

 until sufficient data have been obtained to warrant a definite 

 statement as to the condition of the water at the intakes of the 

 various waterworks which draw from the lower parts of the 

 rivers under investigation. It is believed that the work done 

 shows that the programme given above is the proper one to follow, 

 and this statement of it is therefore made with the hope that it 

 will be found useful in other cases. Considerable experience in 

 selecting conditions and in collecting samples and data will be 

 necessary to make one expert in drawing definite conclusions 

 from the results obtained. 



NOTES AND NEWS. 



The museums and laboratories of the University of Pennsyl- 

 vania are represented by a very considerable exhibit at the Colum- 

 bian Exposition. The University has erected an inclosure on the 

 space assigned to it in the gallery of the Liberal Arts Building, 

 for which the design was contributed by the University School of 

 Architecture. This forms the exhibit of that school. Within 

 this space are contained various collections from the different 

 departments. Notably the Veterinary and Biological. The latter 

 contributes a psychological laboratory, which will be in operation 

 during the summer. The Department of Archasology has sent 

 collections from three of its sections, American, Babylonian, and 

 Egyptian, which are now installed in the gallery. The large col- 

 lection of games and religious objects contained in the Oriental 

 Section of the Museum will be shown in the Anthropological 

 Building. 



— The present interest in subjects connected with the study of 

 sociology has led Professor Charles R. Henderson of the Univer- 

 sity of Chicago to prepare "An Introduction to the Study of the 

 Dependent, Defective, and Delinquent Classes," which will be 

 published about June 1 by D. C. Heath & Co., Boston and 

 Chicago. 



