Art. VII Sriii'.iFF.i,, Orii^i/i <>/ S/^rinx' J'al/fv Gorge. i6i 



broken. Ihi.-ill}- l)K'n(liiii'; intn the c^aN'-likc' iiKiterial ])rcvi()ns!y 

 nicntiiiiu'(l. Tin's nialerial. willi some modifications, conlinnes 

 nntil near a ])oint o]:)posite the south l:ank of the tribut'i.ry wahey 

 when a progressive change to solid rock walls and liottom is noted 

 as first instanced. In .general a consistent arrani^ement of ma- 

 terials is observed on both banks of the cut in this Hood jilain. 



( )nly one ex])lanation for this peculiar arrangement of debris 

 in the luouth of this trilnitary to .Spring- X'alley scenes i)lausiblc. 

 It is readih' accounted for on the hyj^othesis that this drainaj^'C 

 line formerly crossed what is now Spring X'alley, emptying into 

 the stream of the Old \'allev. During glacial times this channel 

 was filled with drift, part of which is now revealed as before men- 

 tioned. That a Hood plain has been forme(l by the Spring X'alley 

 stream at this point and on both sides (the area surrounding C, 

 Fig. 1) is due to the comparatively soft material constituting the 

 debris filling the old channel (tributary to the < )ld X'alley) which 

 it has been able to cut out rapidly at an earlier period of its his- 

 tory. Thus for a ]iart of its course this old valley was exposed, 

 while its drainage was captured at the same time. 



In this connection it may be noted that there is no high rock 

 wall corresponding on the west side to /^ Fig. 1, on the right 

 side. Instead the l)ank shown is of glacial debris deposited over 

 the old channel of the captured tributary S. This trilnitary in 

 its original course to the axis of the ( )l(l X'alley cut off what would 

 otherwise have b^een the northern end of the western rock bank 

 of Spring X'alley. 



The ( )1(I X'alley and this tributary S doubtless were long under 

 the influence of glaciation. The immense depth of debris in the 

 former would alone indicate this, but in the tributary S, particu- 

 larly in the cut through this old filled channel, as stated above, 

 evidence is found of the varying age of the drift. Some of this 

 material, as before described, is clay-like, yellowish in color in- 

 dicative of a long period of exposure and resultant weathering, 

 probably during an inter-glacial epoch. A blue clay also fre- 

 quently outcrops. It is difficult to determine in this limited ex- 

 posure the relative positions of these clays. The blue clay horizon, 

 however, seems to be below the yellow, hence is suggestive of an 

 earlier protected deposit. The appearance of these clays corre- 



