265 Geoloyy and Botany of Northern Pacific Railroad. 



west by a change in the direction of the Cascade^Mountains, and 

 of the representatives of the Coast ranges on Vancouver's Island, 

 is mostly occupied by water, and is known as the Gulf of Georgia. 

 In Washington Territory the Coast Mountains are higher than 

 in Oregon, and have received the local name of [the Olympian 

 range, of which the highest summit is called Mt. Olympus. This 

 range terminates somewhat abruptly, but is apparently continued 

 in the mountains of Vancouver's Island. Through the gap 

 between these and the Olympian range a deep channel is cut, 

 now an arm of the sea, called the Strait of Juan de Fuca. In 

 former times, when this portion of the continent, and probably 

 the whole northwest coast, stood higher above the ocean, this strait 

 was the valley of a great river, which drained most of the western 

 slope of the Cascades in Washington Territory, and had as 

 branches the Skagit, Snoqualme, Dwamish, Puyallop, Nisqtially 

 and various minor streams. During the ice period, this hydro- 

 graphic basin was filled with a great glacier made up of contri- 

 butions from all the surrounding mountains. It flowed out to 

 sea by the Strait of Fuca ; but this channel was far too narrow 

 for it, and it spread all over the southern portion of Vancouver's 

 Island, planing off, rounding over or deeply scoring the rocks in 

 its passage, and leaving its autograph so plainly written that he 

 who runs may read. 



As the glaciers retreated, they left behind a sheet of drift 

 several hundred feet in thickness, partly water worn and strati- 

 fied, partly unstratiiied boulder clay with striated pebbles. 

 These drift deposits formed a plain of which the surface was 

 nearly level. In process of time, the draining streams had cut 

 in this plain a series of valleys all tributary to one which led out 

 through the Strait of Fuca to the ocean. After perhaps some 

 thousands of years, during which the excavation of these valleys 

 progressed, a subsidence of the land or rise of the water-level 

 caused the sea to flow in and occupy the main valley and all its 

 tributaries up to the base of the mountain slopes. Such in few 

 words is the history of the formation of this remarkable system 

 of inlets. They are simply the flooded valleys of a great river 

 and of the branches which formerly joined it, but which now 

 empty into the extremities of the finger like inlets that have 

 partially replaced them. 



