The Pollution of Tidal Harbors by Sewage, With Especial Reference to New York Harbor

Whether the waters are tidal or those of inland lakes, the fundamental considerations regarding harbor pollution are the same, but the effects are accentuated in sea-coast harbors for several reasons: 1. The oscillations of the tidal flow alternate with periods of slack-water when solids settle rapidly to the bottom and form sludge banks. 2. The presence of salt in the water tends to precipitate the soaps in the sewage, making the effluent noticeable by its milky appearance and promoting further sedimentation. 3. Owing to the greater specific gravity of sea water, the warmer sewage rises rapidly to the top and spreads out in a thin layer, diminishing to a film of sleek which covers a large and readily distinguished area on the surface. 4. As sludge deposits decompose, sulphureted hydrogen is formed in greater abundance in salt water than in fresh water, owing to the breaking down of the sulphates contained in the sea water. Sulphureted hydrogen is known as the most characteristic of the offensive odors of putrefaction.