136 THE ICE AGE IN NORTH AMERICA. 



the streams crossed by the railroad. At Tacoma, on Puget 

 Sound, the milk-white water, coming down from distant gla- 

 ciers in Mount Tacoma, struggles with the dark-blue water 

 of the sound for the occupancy of the harbor, and gives the 

 surface of the bay the nondescript appearance of an im- 

 mense slice of marble-cake. As one passes the mouth of 

 the Stickeen River beyond Fort Wrangel, in Alaska, the 

 line of demarkation between the clear waters of the ocean 

 and those of the glacier-laden currents of the river is as plain 

 as that between the water itself and the shore. One of the 

 most interesting occupations of the leisure hours of our long 

 encampment in Glacier Bay was to watch this struggle for 

 occupancy between the milk-white water of the four sub- 

 glacial streams pouring into the inlet, and the pure blue 

 waves urged against it by the recurring tides of the ocean. 

 With a rising tide of twenty-two feet, the line of demarka- 

 tion between the glacial water and the waters from the Pacific 

 moved alternately backward and forward over the inlet for a 

 distance of one or two miles, and in the shallow water, miles 

 away, the screw of the steamer brought to the surface great 

 quantities of the sediment which is rapidly filling up the bay. 

 When one considers the constancy of the operation of 

 this cause during all glacial time, he may well be pardoned 

 for regarding the glacial debris still remaining upon the con- 

 tinent as but an insignificant remnant of the total amount 

 transported and deposited by glacial action. During the 

 whole continuance of the Glacial period in North America, 

 subglacial streams must have sent their turbid currents down 

 through every New England outlet, and through the Hud- 

 son, the Delaware, the Susquehanna, and all the northern 

 tributaries of the Mississippi. The terraces marking these 

 glacial water-courses retain simply a part of the coarser ma- 

 terial transported ; the fine material went constantly onward 

 to the sea, helping to build up the immense delta of the lower 

 Mississippi, and to line the whole coast of the Atlantic with 

 a deposit of fine sediment ready at some day to rise above 

 the surface as fruitful soil. 



