Itinerary ii 



are deposited by the swift waters along the border of the main 

 channels while the finer superimposed strata are laid down in the 

 slack water on the inner margins of curves during flood stages, and 

 it is here that pieces of ice floating down on the spring floods be- 

 come stranded as the waters recede, and melting deposit any freight 

 in the shape of fragments of fossil bones, teeth, etc., that may be 

 frozen within or borne upon them. Below the level of flood these 

 bars present a surface of gravels, sands, and mud bare of vegetation 

 but strewn over with stumps, logs, and drift brush. Back of this 

 comes a strip covered with grasses and a variety of equisetum called 

 " goose-grass " because it forms the chief food of these birds during 

 their molting season. Above this belt comes a growth of young 

 willows which as they recede from the river increase to a height of 

 twenty to thirty feet. Mingled with the willows and replacing them 

 on the landward side are clumps of alders and groves of poplars 

 which in turn are succeeded on higher, better drained lands by 

 spruce forests extending away to mingle with the birch growing on 

 the distant hills. Below the depth of a foot or two the soil is 

 everywhere frozen. 



Above the Yukon Flats the Porcupine flows from a considerably 

 contracted valley called " the Ramparts." This is a name intro- 

 duced by the northern fur-traders to designate a contracted, walled, 

 or caiion-like valley and has been applied by them to similar physio- 

 graphic features on the Mackenzie, Porcupine, and Yukon, rivers. 

 On the Porcupine, Upper and Lower Ramparts are differentiated 

 and the portions of the valley so named are very picturesque. In 

 passing through the Ramparts the river contracts considerably, not 

 exceeding seventy-five yards in width in places. The current be- 

 comes more rapid, flowing from three to four and a half miles an 

 hour with occasional short riffles where the velocity is much greater, 

 being estimated at seven or eight miles per hour, but there are no 

 obstructions or rapids which would prevent a small light-draft 

 steamer with requisite power from navigating the river (plate i). 



The change in topography in ascending from the Yukon Flats 

 into the Lower Ramparts is ushered in gradually by a belt of Pleis- 

 tocene deposits several miles wide rising thirty to fifty feet above 

 the river, followed by several ranges of low hills leading up to the 

 abrupt walls of the entrance to the contracted portion of the valley. 

 The river flows through the Lower Ramparts for about twenty- 

 five miles. The rocky walls, generally disconnected and low, are 

 composed for the most part of limestones seldom abruptly developed 

 on both sides of the river so as to form a canon. Thus a shore is 



