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FLOW OF STREAMS. The total flow of the streams in 1891 was in excess of the normal yearly flow, but the seasonal distribution was very uneven, being excessive in the first four months of the year and less than the normal in all of the other months. This is shown by the following table, in which a comparison is made between the flow of the Sudbury River during each nionth in 1891 and the normal flow of the same river for each month, as deduced from thirteen years' observations, from 1879 to 1891 inclusive:

Table showing the Average Monthly Flow of Sudbury River for the Year 1891

in Cubic Feet per Second per Square Mile of Drainage Area, also Departures from the Normal Flow.

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The next table shows the weekly fluctuations during 1891 in the flow of two streams, namely, the Sudbury and the Merrimack. The flow of these streams, particularly the Sudbury, will serve to indicate the condition of other streams in eastern Massachusetts :

Table showing the Average Weekly Flow of the Sudbury and Merrimack Rivers, in

Cubic Feet per Second per Square Mile of Drainage Area, for the Year 1891.

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Occasional measurements of the flow of other streams have been made, and the results may be found on previous pages, as follows: Blackstone River, page 277; North Branch of Nashua River, pages 307 and 308 ; South Branch of Nashua River, page 309; Neponset River, page 322.

EXAMINATION OF SPRING WATERS.

EXAMINATION OF SPRING WATERS.

There is a large quantity of spring water sold throughout the State, particularly in cities and towns where the regular water supply is thought to be unsatisfactory, or where the water, as is not infrequently the case with surface-water supplies in the summer time, has an unpleasant taste and odor.

A considerable number of these spring waters were collected for examination during the summer of 1891, and at the same time a careful inspection of the surroundings of the springs was made, to discover possible sources of pollution. Not only is there a large sale of spring waters as such, but there is also a large amount consumed in bottled form, as soda water and other effervescing drinks.

As the result of this investigation, it was found that some of the springs were situated in regions nearly or quite free from population, where the land was not under cultivation, and the chemical examinations of these waters showed them to be of the highest purity. Other springs were situated in populous districts, or had near them direct sources of pollution, and the water gave evidence, on chemical analysis, that it had, in its course, received a large amount of drainage from sinks, cesspools, privies or stables. In most of the springs of this character which were examined the water showed, however, a high degree of purification by filtration through the ground.

The results of the chemical and bacteriological examinations are given below. In accordance with the system of classifying waters adopted in the Report on the Water Supplies of the State (see Special Report on the Examination of Water Supplies, 1890, pages 679 to 716), these spring waters have been divided into three groups, based on their chlorine contents.

The first group includes the normal waters and those in which the chlorine is not over 0.20 parts per 100,000 in excess of the normal; the second, those in which the excess of the chlorine is from 0.21 to

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