223. Fish and oysters.—In the wintertime, the canning factories of Baltimore are busy canning oysters, for which Baltimore is the greatest market in the world. The oyster lives at the bottom of shallow waters, from the Gulf of St. Lawrence to the Gulf of Mexico. The chief oystering centers (Fig. 207) are the Chesapeake and Delaware bays and Long Island Sound. Every au tumn and winter, hundreds o f boats, mostly two masted schooners (Fig.223), go out on these waters to bring back oysters. Fresh oysters are sent in their shells or in buckets to many parts of the United States. Like vegetables, they are also canned.
224. Oyster -farming.
Recently men have begunwhat is called oyster-farm ing. The baby oyster swims around in the water until it finds a pebble or an old oyster shell, or even a stick of wood, on which it can settle safely and be out of the .mud. Here it sticks fast and rapidly makes a shell, eating whatever the currents bring within reach. If the baby oyster happens to settle in the mud, it is smothered. If it fastens to something firm and hard, and all goes well, it will grow big and may lay a great many eggs, which hatch into other little oysters.
The oyster-farmer leases from the state a piece of sandy-bottomed bay, though no oysters may be growing there. Then he drops overboard the branches of trees, or old oyster shells. The little floating oysters will settle on such things, and in a few years the oysters will have grown big enough to be taken up with dredges and sent to market. (Fig. 207.) 225. Seashore vacations.— Another important city in this region is Atlantic City. It has just one industry—that of tak ing care of people who want a vacation beside the sea. It is the largest city in the world where the only industry is that of taking care of visitors. Peo ple love the ocean. They love to walk along the beach, to smell the salt air, to feel the fresh cool breeze, to pick up shells in the sand, and to watch the tide creep up and down, as it does twice a day on all the seashores of the world. They love to bathe in the cool ocean and to be tossed about by its never-ceasing, roaring waves. The shores of New Jersey, Long Island, and Cape Cod are fast becoming rows of towns where people from the hot interior seek refuge from summer heat.
26. Sea breezes.—The sea beach is a place where one can nearly always be com fortably cool. When a stranger who is staying at the seashore in the North Atlantic Coast Plain takes a walk about 9:30 o'clock on a summer morning, he is almost sure to think, " It is getting hot. I fear this will be
a very hot day." Suddenly he feels a breeze blowing in from the sea. It is a cool breeze, and it blows all day. What has happened? As the hot morning sun beats upon the sea and upon the salter, eatid bedoinei nitich hotter than does the water. The sun's rays sink deep into the sea, so they cannot warm its surface very much; but they heat the surface of the sand, partly because they cannot sink into sand as they can into water. . Besides, it takes more heat to heat water than it does to heat earth to the same temperature. Thus an hour or two of sunshine makes the sand very hot, while it heats the water only a very little. Because the sand of the beach is heated, the air over it becomes hot, too, and begins to expand (Sec. 66). After a few hours the heat has expanded the air on the beach so much that it is lighter than the cooler air over the sea near by. Then the heavy air over the sea pushes the lighter air upward and flows toward the land to take its place. The lighter air over the beach rises just as a cork in a dish rises when water is poured in.
When the cool sea air flows in to take the place of the hot beach air, we have a sea breeze. The sea breeze blows on the seashore of nearly all warm places, and so the seashore is much cooler in summer than places inland. When people are sweltering from heat at Philadelphia, Washington, or Pittsburgh, on a summer day, a cool, pleasant breeze may be blowing along the seashore. A cool sea breeze may be enjoyed from Cape Cod to North Carolina, from North Carolina to Florida, and on thousands and thousands of miles of seashore in all warm continents, on many, many islands, and on the shores of many lakes.
Land breeze sand cools off much faster than water, the seashore sometimes gets cooler at nights than the sea. Can you explain how it is that there is a breeze from land to sea at that time? Sometimes the west wind blows so strongly in the North Atlantic Coast Plain that instead of a sea breeze there is a land breeze by day. It is a hot breeze, and it blows millions of mosqui toes out of the swamps. It is not pleasant then to be at some of the beach towns. Fortunately the land breeze does not often blow.