helped. Probably the best natural port in the state is the lower Thames River, and it harbors Connecticut's only naval base and Electric Boat, one of only two shipyards in the country that build submarines.

An important factor in the creation of Connecticut's saw-toothed coastline was glaciation or, more precisely, deglaciation. The formation of an ice cap 6000 to 7000 feet thick covering half of North America (and nearly as large an ice sheet in Europe) took a lot of water. Weather patterns carried this water from the ocean and fed it to growing glaciers in the form of snow. Consequently, sea level dropped more than 250 feet, turning much of the shallow continental shelf regions just offshore into dry land. Rivers stretched their courses across this newly exposed land to reach the lowered ocean, cutting deep valleys into the shelf. When deglaciation finally began about 16,000 years ago, the melting ice restored water back to the ocean. As more and more water returned, the ocean swelled and sea level advanced landward, always furthest up the deep river valleys. Today, sea level has risen to approximately the same height as in preglacial times but has flooded the lower reaches of many valleys, giving Connecticut what is known as a "drowned coastline'

Drowned coastlines are not particularly unusual. The entire East Coast of North America has been drowned by the encroaching sea. For example, Chesapeake and Delaware bays are drowned valleys, even though they look very different from any drowned valley in Connecticut. These huge bays are great rootlike things with many branches flooding deep inland. But in Connecticut the drowned valleys are long and straight with few branches; the lower Connecticut River is a good example. The difference in appearance of the southern drowned valleys results from their being cut into loose Coastal Plain sediments rather than into the hard rock of Connecticut's Coastal Slope.

Many Connecticut rivers - the Pawcatuck, Mystic, Niantic, Connecticut, Thames, Quinnipiac, Housatonic, Pequonnock, Saugatuck, Norwalk, and Mianus - have been flooded quite some distance inland. These are tidal rivers whose water levels respond to the rise and fall of tide. Native Americans recognized the important difference in the character of these rivers; the syllable "tuck", and its corruption "tic", contained in five of the river names means "tidal river"' Tide makes its

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