122 TRANSACTIONS OF THE [FEB. 18, 
than thirty-five feet ; nevertheless the direct transmission of the 
sun’s heat and light is the source of most active decomposition 
and organic growth. As the proposed Quaker Bridge dam is to 
be very deep, it will be proportionately free from objection on 
this score. 
But there is another characteristic feature of Croton water, in 
regard to which the depth of the proposed reservoir. will be of 
very little effect. Our city water is originally a peaty water, as 
may be seen in the streams of Westchester County which supply 
the Croton system. ‘The brown color of these waters disappears 
on oxidation, but it requires very prolonged action of air, and 
probably of sunlight, to remove the color to any great extent. 
In fact the water is never entirely colorless, or nearly so, if it be 
observed in a layer as little as one foot in depth. As we draw 
it from faucets in the city, the color is usually perceptible, even 
in an ordinary goblet, and often quite pronounced. These 
variations in tint, apart from the mere cloudiness or muddiness 
due to suspended matter, are dependent upon temperature, rate 
of flow, and especially upon season, the depth of color being 
greatest in autumn. The latter fact is probably due, in part, 
to decay of leaves, but also to acceleration, by heat, of the decom- 
position of peaty matter, through which soluble products are 
formed ; and this result is an accumulated effect which is most 
apparent only after the summer has closed. The Central Park 
reservoirs are almost as brown at times in the fall as the waters 
of the Croton or its tributaries. Now, the surface of water ex- 
posed to air and light—and therefore the facilities for oxidation 
—will be less in a deep reservoir, in proportion to the volume of 
water, than in a shallow one. We cannot therefore expect any 
improvement in the color of Croton water, as we receive it in 
the city, from the building of the great dam. 
Again, the suspended matter of Croton water differs very 
much in character at different seasons. In winter it is compara- 
tively trifling in quantity ; in spring it is more abundant, often 
excessive, but made up principally of suspended clay, or clay 
made flocculent by small quantities of organic matter, which 
readily subsides. In summer, especially late in the season, how- 
ever, it is largely organic, and is so light and flocculent that much 
