(3) The Ocean as an Aid to Health.—The Sea Coast.—As compar atively few people sail the sea, the coast is the place where the ocean exerts its influence directly upon the greatest number of persons. There the oceans are a wonderful aid to health in five chief ways: (a) Extremes of temperature are rare; (b) extreme dryness is also fare; (c) small short-lived changes of temperature from day to day and even from hour to hour are frequent; (d) the variety and beauty of the seashore tempt people to engage in outdoor sports such as bathing, fishing, and walking; (e) the ocean is a wonderful purifier, and not only carries away but destroys most impurities brought into it from the land.
The first three of these favorable conditions all arise from the winds that blow from the sea. Almost as soon as a land breeze begins to cause extreme heat in summer or extreme cold in winter, a sea breeze brings a change and causes the temperature to moderate. The only unfavorable effect of the seacoast upon health in temperate latitudes arises from the fact that during " hot spells " in summer the dampness of the sea makes the heat harder to bear than when the air is dry. Prostrations and deaths from heat in New York City, for example, are often due to this cause, but such occasions are so rare that they are a small matter compared with the benefits derived from being near the sea. The combined effect of all five upon health is to cause much of the shore from Maine to Florida to be lined with sum mer cottages.
Recreation on a Submerged Coast.—In Maine the slimmer visitor delights in the beauties of a submerged coast, where innumerable deep bays dotted with picturesque rocky islands tempt him to sail and en joy their beauty, even if he does not care to catch the fish which abound in the cold water. The intervening peninsulas with their gar ment of spicy pine forests and their rugged cliffs worn by the ever gnawing waves tempt him to go on long walks or to sit at the top of some bluff and watch the dashing waves, or catch fish from the rocks. The materials worn from the rocky cliffs on the outer part of the pen insulas and capes are carried by the currents to the heads of the innumerable bays, and there form little beaches where boats can safely be drawn up, and where on sunny days the water may become warm enough to permit bathing.
Recreation on an Emerged Coast —Farther south in Florida the fact that the coast has emerged gives rise to broad sandy beaches. The surf rolls in magnificently to the pleasure not only of the spec tators who sit in the sun on the beach, but of the bathers who can enjoy the warm water for hours each day. Children delight to dig in the dry sand near high tide level, and watch the pelicans open their enormous bills. Between the levels of high and low tide the damp
beach is so hard and smooth that it offers almost ideal place for automobile races. Boating is not so easy as on the submerged coasts, farther north, for only where streams enter the ocean can even small boats be kept. When the boats get out to the sea, however, they afford the finest kind of sport in catching fish like the baracuda.
A few weeks of ocean air and pleasant recreation on almost any seacoast of the United States at the right season make one feel full of energy and ready for all sorts of work. It must not be overlooked, however, that part of the benefit is due to the change from home conditions, together with the outdoor life, and the opportunities for new forms of recreation.
How Coasts Benefit the Health of the Tropics.—In tropical coun tries the cooling effect of the sea is especially important. Winds from the sea temper the constant heat and make people feel much more like work than is possible for those who live farther inland. The ocean winds also drive away the mosquitoes and other insects which are so great a menace to health and comfort. For these reasons a surprisingly large part of the people of equatorial Africa, for example, have placed their high-pitched cottages along the shore where the afternoon sea breeze serves as the " doctor." How the Ocean Disposes of Sewage.—Another important function of oceans is their help in disposing of sewage. One of the most ex pensive duties of the modern cities is to get rid of the sewage in such a way that it will do no harm. In general the sewage is conducted into some neighboring body of water. If the water is in motion the sewage is carried away and greatly diluted. Thus in a short time the water purifies itself so that even the most careful analysis fails to show pollution. If sewage is conducted into a body of standing water without marked currents, however, the water becomes polluted and may prove a source of grave danger. Chicago found this to her cost when she tried to dump sewage into one part of Lake Michigan and take drinking water from another. She had to spend about $40,000,000 in order to build a drainage canal deep enough so that the dirty Chicago River, into which the sewage pours, would flow toward the Mississippi River instead of toward the lake. On the sea coast, especially where there are strong tides, the difficulties of disposing of sewage are reduced to a minimum. In some coast cities such as Boston, for example, part of the sewage is held in reser voirs until strong outgoing tidal currents have developed. Before the turn of the tide it has been carried so far that it has become mixed with an enormous body of ocean water and has become harmless.