ber of sampling points exceeded 1,500, and the number of samples collected at them was over 18,000. The following table shows the location of the laboratories, the waters examined, the dates of the examination, the number of sampling points, and the total number of samples:

Points for the collection of samples were carefully located, but positions which might show exceptional pollution at sewer outlets were avoided, except in certain cases where information touching them was desired for special reasons. Owing to the extraordinary amount of navigation on these waters, fixed buoys were not feasible for the purposes of locating sample collection points and the work was carried on by a time and course method, the samples being collected at prescribed time intervals and along definite courses laid down on the charts of the waters. In swift-running water, as in the Niagara, Detroit, and St. Clair Rivers, diagonal courses were necessary in order to give some length to the cross sections and allow sufficient time intervals between the taking of the samples. The various field parties were all furnished with United States War Department maps showing a great deal of the topography of the areas under investigation, and also with copies of the sewer maps. for the adjacent municipalities.

In addition to the examination at these points, samples were collected to show the relation between local situations and municipal water supplies and to ascertain the character and extent of the pollution which might be due to vessels navigating boundary waters. Both surface and deep samples were simultaneously taken at certain

points in the St. Clair, Detroit, and Niagara Rivers in order to determine the effect of stratification. While some situations show definite stratification, it may be accepted in interpreting the results that for the waters under investigation surface samples measure directly the extent of bacterial pollution.

The investigations were essentially bacteriological and the work was continued at each sample-collection point during a period of time sufficient to observe the quality of water, irrespective of minor variations.

Other data collected.

Besides this bacterial examination, some float and temperature observations were made and inquiries were carried on and data collected and compiled as to area, population, location of water-supply intakes, quantity of sewage discharged, for each of the several municipalities in the areas under investigation.

Meteorological data relative to the several points of investigation for the periods of examination were furnished by the meteorological departments of the United States and Canada, and the State and provincial health bodies assiduously supplied the commission with such vital statistics as were available. From these statistics the death rate from typhoid fever per 100,000 has been computed for each of the municipalities either abstracting water from or draining into the boundary waters.

The immense amount of information thus gathered and presented to the commission appears in the report of the sanitary experts. Maps were prepared to show the location of sample collection points, and charts and tables to show the bacterial counts, B. coli averages per 100 cubic centimeters for each of the sample collection points, together with the dates of collection and the maximum amounts encountered during the period of examination. This material was published with the progress report of the commission under date of January 16, 1914.1

Investigations at sittings of commission.

With the object of obtaining information in addition to what had been gathered by the sanitary experts in their exhaustive investigation, the commission held sittings at many places along the border and took the evidence of a large number of people who were acquainted with the insanitary conditions of several of the districts affected by pollution. Members of the commission also personally examined most of the points where pollution was strongly complained of.

Messrs. Streeter and Powell, as a committee of the commission, took evidence at Buffalo in the month of June, 1913, touching the

1 Progress report of the International Joint Commission on the reference by the United States and Canada in re the Pollution of Boundary Waters. Including report of the sanitary experts. 1914.

extent of pollution in the Niagara River and the effect of this pollution upon the riparian towns on the United States side of the river.1 Subsequently, during the months of September, October, and November, 1914, and the months of June and August, 1916, meetings of the commission, at which the pollution of boundary waters was inquired into, were held at a number of places along the Niagara, Detroit, and St. Clair Rivers.2, 8

itary engineers at New Yorn.

In order that the commission should, in a matter of such vital importance as was being investigated, know the attiConference with san- tude of leading exponents of sanitary science, it prepared and submitted a series of questions to a number of sanitary engineers of large experience and wide reputation in the United States and Canada, namely: Mr. George W. Fuller, of New York City; Prof. Earle B. Phelps, of the United States Public Health Service; Mr. George C. Whipple, of Harvard University; Mr. W. S. Lea, of Montreal; Mr. T. J. Lafrenière, of the Provisional Board of Health of Quebec; and Mr. F. A. Dallyn, of the Provincial Board of Health of Ontario. These six engineers afterwards, on the invitation of the commission, attended a conference with it in the city of New York. They are hereafter referred to as the "advisory engineers." Some days were spent in their examination, but the lengthy testimony they gave was condensed by them into a résumé of 14 points, as follows:

Résumé of testimony.

5

1. Speaking generally, water supplies taken from streams and lakes which receive the drainage of agricultural and grazing lands, rural communities, and unsewered towns are unsafe for use without purification, but are safe for use if purified. 2. Water supplies taken from streams and lakes into which the sewage of cities and towns is directly discharged are safe for use after purification, provided that the load upon the purifying mechanism is not too great and that a sufficient factor of safety is maintained, and, further, provided that the plant is properly operated.

3. As, in general, the boundary waters in their natural state are relatively clear and contain but little organic matter, the best index of pollution now available for the purpose of ascertaining whether a water-purification plant is overloaded is the number of B. coli per 100 cubic centimeters of water expressed as an annual average and determined from a considerable number of confirmatory tests regularly made throughout the year.

1 Preliminary report of committee having general supervision of the investigation relating to the pollution of boundary waters; with documents * relating to the petitions of the Erie and Ontario Sanitary Canal Co. for permission to divert 6,000 second-feet from Lake Erie. 1913.

Hearings of the International Joint Commission in re remedies for the pollution of boundary waters between the United States and Canada. 1914.

Hearings of the International Joint Commission in re remedies for the pollution of

boundary waters between the United States and Canada. 1916.

• Conference with sanitary engineers at New York City, May 26 and 27, 1914. Résumé of testimony of consulting sanitary engineers in the matter of the pollution

of boundary waters, New York, 1914.

4. While present information does not permit a definite limit of safe loading of a water-purification plant to be established, it is our judgment that this limit is exceeded if the annual average number of B. coli in the water delivered to the plant is higher than about 500 per 100 cubic centimeters, or if in 0.1 cubic centimeter samples of the water B. coli is found 50 per cent of the time. With such a limit the number of B. coli would be less than the figure given during a part of the year and would be exceeded during some periods.

5. In waterways where some pollution is inevitable and where the ratio of the volume of water to the volume of sewage is so large that no local nuisance can result, it is our judgment that the method of sewage disposal by dilution represents a natural resource and that the utilization of this resource is justifiable for economic reasons, provided that an unreasonable burden or responsibility is not placed upon any water-purification plant and that no menace to the public health is occasioned thereby.

6. While realizing that in certain cases the discharge of crude sewage into the boundary waters may be without danger, it is our judgment that effective sanitary administration requires the adoption of the general policy that no untreated sewage from cities or towns shall be discharged into the boundary waters.

7. The nature of the sewage treatment required should vary according to the local conditions, each community being permitted to take advantage of its situation with respect to local conditions and its remoteness from other communities, with the intent that the cost of sewage treatment may be kept reasonably low.

8. In general, the simplest allowable method of sewage treatment, such as would be suitable for small communities remote from other communities, should be the removal of the larger suspended solids by screening through a one-fourth inch mesh or by sedimentation.

9. In general, no more elaborate method of sewage treatment should be required than the removal of the suspended solids by fine screening or by sedimentation, or both, followed by chemical disinfection or sterilization of the clarified sewage. Except in the case of some of the smaller streams on the boundary, it is our judgment that such oxidizing processes as intermittent sand filtration and treatment by sprinkling filters, contact beds, and the like, are unnecessary, inasmuch as ample dilution in the lakes and large streams will provide sufficient oxygen for the ultimate destruction of the organic matter.

10. Disinfection or sterilization of the sewage of a community should be required wherever there is danger of the boundary waters being so polluted that the load on any water-purification plant becomes greater than the limit above mentioned.

11. It is our opinion that, in general, protection of public water supplies is more economically secured by water purification at the intake than by sewage purification at the sewer outlet, but that under some conditions both water purification and sewage treatment may be necessary.

12. The bateriological tests which have been made in large numbers under the direction of the International Joint Commission indicate that in most places the pollution of the boundary waters is such as to be a general menace to the public health should the water be used without purification as sources of public water supply or should they be used for drinking purposes by persons traveling in boats.

13. It is our judgment that the drinking water used on vessels traversing boundary waters should not be taken indiscriminately from the water traversed, unless subjected to adequate purification, but should be obtained preferably from safe sources of supply at the terminals.

14. While recognizing that the direct discharge of fecal matter from boats into the boundary waters may often be without danger, yet in the interest of effective sanitary administration it is our judgment that the indiscriminate discharge of unsterilized fecal matter from vessels into the boundary waters should not be permitted.

gations.

These views of the advisory engineers were given after most mature consideration on their part, and not only have they been of great assistance to the commission in arriving at the conclusions and recommendations expressed in this report, but their thoroughness and exhaustiveness have been recognized by scientists on this continent and in Europe, frequent applications having been made to the commission for copies of both the testimony and the résumé. It was necessary that the commission should form some reliable estimate of the cost of installing the requisite Engineering investi- remedial works, and it determined to carry on its investigations in such detail that the engineering possibilities and difficulties would be fully considered and the cost of the ultimate projects determined within reasonably close limits. Prof. Earle B. Phelps, of the United States Public Health Service, was engaged as the commission's consulting engineer and was put in charge of the investigation. Engineering offices were established at Detroit and Buffalo, each office comprising a small but wellorganized force, under Prof. Phelps' supervision, but in immediate charge of a district engineer. The Detroit office had charge of the investigation in the cities and towns bordering upon the St. Clair and Detroit Rivers, and the Buffalo office had charge of the investigation along the Niagara River. The investigations covered the following cities and towns:

In the United States: Port Huron, St. Clair, Marine City, Algonac, Detroit, River Rouge, Ecorse, Ford City, Wyandotte, Trenton, Lackawanna, Buffalo, Tonawanda, North Tonawanda, Lasalle, Kenmore, Niagara Falls, Lewiston, and Youngstown.

In Canada: Sarnia, Ford, Walkerville, Windsor, Sandwich, Amherstburg, Fort Erie, Bridgeburg, Chippewa, Niagara Falls, Queenston, and Niagara-on-the-Lake.

All of these cities and towns were asked to assist in the investigations in which they were respectively concerned. The examinations at Detroit and Buffalo were of much greater magnitude 'than the others, and this fact, coupled with the wish of the commission that these cities should be associated with the investigation in which they were interested, led to an invitation being extended to their officials to collaborate with the consulting sanitary engineer in the prosecution of his work; and the commission expresses its apprecia tion of their sympathetic and efficient cooperation.