From the Mexican border to Canada the 1，3oo miles of Pacific coastline<br >offer only seven natural harbors-Long Beach， San Diego， Monterey，<br >San Francisco， and Eureka， California， and Willapa Bay and Grays<br >Harbor， Washington. But the meagerness of shelter does not gravely<br >affect shipping， for the Pacific Ocean in those latitudes lives up to its<br >name. From the Canadian border north， however， coastal piloting is a<br >different matter.<br > Under prevailing westerly winds， stormy North Pacific waters off the<br >coast of Japan push up great rollers that march in stately procession，<br >building in size and power， across 4，000 miles of open sea to crash on the<br >northwesterly coast of North America.<br > Precisely on that wild coast， 4~ million years ago nature came to the<br >rescue of mariners-to-be. A land mass called Cascadia then stood west of<br >where the present mainland stands. In a gigantic convulsion it sank<br >beneath the sea， leaving exposed only its mountaintops as Vancouver<br >Island， the Queen Charlotte Islands and the other barrier islands that<br >stand between rollers from Japan and the mainland. The sheltered<br >channel inside the barrier islands threads x，ooo miles northward from the<br >Washington shore of the Strait of Juan de Fuca through British<br >Columbia and Alaska to Skagway.<br >