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Table I a.—Examination of Merrimack River. [Results expressed in Grains per U. S. Gallon.]
1 For remarks see Table I.
*The unfiltered water gave: inorganic, 1.17; organic, 1.40; Total, 2.57.
What becomes of all the waste material daily thrown into the waters of the Merrimack?
This question has already been somewhat discussed in a previous report, but it may be well to recapitulate or re-state the facts and opinions there brought forward.
The principal causes which contribute to the apparent'disappearance of the refuse received by the river are three, and these, in what I conceive to be the inverse order of their importance, are oxidation, deposition and dilution.
Oxidation.—Although it is not practicable, in the case of a running stream like the Merrimack, to trace the progress of the destruction of the organic material by oxidation, yet there is no doubt that a certain amount is so destroyed. The presence of nitrogen in the form of nitrites and nitrates is mainly due to the oxidation of nitrogenous organic material. The amount of nitrogen thus existing in the Merrimack, even below Lawrence, is so small that its determination would not afford much that is valuable as data of comparison. In the last report of the Board, the reasons are given which lead to the belief that the effects of oxidation have been overrated, although they are not, on the other hand, to be depreciated. In this connection I made an attempt to ascertain whether any difference could be perceived in the amount of oxygen dissolved in the water at various points in the stream, such as above and below Lawrence and above and below Lowell. The results obtained may be found in the Tables I. and Ia. As far as the direct end which was in view when the inquiry began is concerned, the results are negative. It is true that on September 8th the amount of oxygen in the river above Lowell (see No. 108) was found to be 3.32 cubic centimeters to the liter, while below the city (No. 109) only 1.89 cubic centimeters was found; but determinations made at other times showed a smaller amount above the dam; and, moreover, at the time No. 108 was examined, a stiff breeze was rufiling the surface of the river. Although a very considerable number of determinations, made at frequent intervals orer a sufficiently long period of time might show some decrease of oxygen below the manufacturing towns, I did not feel that sufficient encouragement was afforded by the results obtained to warrant, at the present time, a very extended series of experiments. The total amount of oxygen seems very small,-much smaller than we might expect. Moreover, the amount was found to be quite uniform throughout the mass of the water, as may be seen by comparing Nos. 145 and 147, where water was taken not only from the surace, but also from a depth of some twelve feet.
Deposition.-Much waste material thrown into rivers is made up wholly or in part of substances insoluble in water. A portion, and a very considerable portion, even in a running stream, is deposited upon the bottom or stranded upon the
' banks. This deposition can often be very plainly observed in the immediate neighborhood of the points of discharge. Other chemical changes besides that of oxidation, alluded to above, take place, especially where the refuse is that from manufactories. Waste liquors from different manufacturing operations meet and cause the formation of new and, in many cases, of insoluble compounds. At the time of the spring freshets, much that during the summer may have been depos