212 
Tlic American Geologist. 
October, 1898 
Diagram No. 3. 
ice as presenting the easiest avenue of escape across the ram- 
part; i. e., the lowest point, and was subsequently deeply ex- 
cavated by the long continued and gradually concentrated 
ice-flow. Today its superficial features of kettle-holes and 
morainic banks have not been obliterated nor even noticeably 
modified by subsequent drainage. 
(i). These recessional deposits are fairly characteristic of 
coulees of the third class, as also of the second. Antwine's 
coulee, which connects the Methow river at a point four miles 
above its mouth, with the Columbia river, over ten miles 
away, is so obstructed by local and foreign boulders that its 
passage is with difficulty effected on horse. Moreover, the 
lower or southern extension of this coulee is bounded by 
walls of terrace material, which were evidently accumulated 
at a time when the occupation of the Columbia gorge by the 
still moving Okanogan glacier prevented the free escape of 
drainage waters. 
(2). Below the end of Antwine's coulee there exists an- 
other extending in substantially the same direction as the 
main Columbia valley. This latter is unique from the fact that 
its general outlines were probably determined by a split in the 
mountain, the portion toward the river falling away and re- 
vealing a fissure a thousand feet in depth, and scarcely wider 
