REPORT OF THE DIRECTOR I919 61 



velocity to carve out the depression it occupies in part. The lakes 

 which are the source of the present stream are of sufficient area to 

 equalize the rainfall run-off discharge of their drainage area so that 

 the stream does not fluctuate between flood and drouth as would 

 normally be the case with a stream not having such storage reservoirs 

 at its head. Hence it may be assumed that the stream never fills its 

 wide channelway to the banks, as indeed is evidenced by the fact 

 that very low bridges have been built across it, houses placed near 

 the water's edge and that forest trees have grown up in the channel 

 bottom. 



It appears, therefore, that the Tioughnioga channel in this section 

 was formed when the stream carried a much larger body of water, 

 that is, when it was fed primarily by the outflow from the Cardiff lake, 

 ponded behind the Tully morainic barrier. This water was probably 

 relatively free of debris when it reached the part of the Tioughnioga 

 course under discussion but here it probably received accessions of 

 sediment-laden water coming over the Otisco outwash. At a later 

 date this water, too, may have cleared up on becoming the outflow 

 of the highest level lake in the Otisco valley and the combined volume 

 of two such large drainage basins would suffice to create a stream of 

 considerable magnitude, one that could amply fill the channel from 

 bank to bank and scour out a typical flat-bottom lake outflow course. 

 Truncated spurs. One feature of the topography due to the 

 glacial occupation yet remains to claim attention. This is the con- 

 spicuous facetting of the slopes of spurs that formerly projected with 

 rounded shoulders into the main valley, but which have been planed 

 off by the ice erosion so that the through-valley Onondaga-Tiough- 

 nioga depression now has a straight line course. On the topo- 

 graphic map the truncated spur phenomenon is well illustrated by 

 the east side of Toppin mountain across the valley from Preble and 

 again on the spur to the north of Preble. In the photograph 

 (plate 20) are shown both the upper end of the Tioughnioga (south 

 continuation of the Onondaga valley) valley (on the right) and the 

 south end of the Otisco valley (on the left) with the rock hill of the 

 divide spur rising between them. The summit and the hollow on the 

 south side of this spur, the lee slope with respect to the glacial onset, 

 preserve, essentially, the preglacial contours of the country in their 

 soft, rounded, mature curves. The east end, however, has been 

 abruptly cut off, as though sliced through with a huge knife, and this 

 is a characteristic feature of such spurs where they were affected by 

 the ice scour. While difficult to photograph effectively, such spurs 

 are a very conspicuous element in the scenery of the area and arrest 

 the attention of even the casual tourist. 



