Davis — Terraces of the Westfield Biver^ Ifass. 91 



far forward toward the Talley axis; this southern sweep is 

 therefore the only one that has consumed all the sontliern ter- 

 races at intermediate and low levels. The abandoned channel 

 of the sweep is still swampy and the enclosing scarp is still 

 nneven with landslides, so lately has the river been withdrawn. 

 It is natural enough that the river should not have swung so 

 far south at higher levels, for the guiding ledge, M, is rather 

 low ; it was not encountered until the river had cut down its 

 flood plain nearly to the present level. 



Inasmuch as the southern sweeps, S' and P. seem to have 

 been guided by the northern ledges, K^ and M, it is natural 

 to find the unconsumed remnant of the terrace between the 

 two sweeps in the form of a cusp, Q. This cusp is about 

 forty -five feet high. It is entirely undefended and might, 

 therefore, at first sight be classed with free cusps, and re- 

 garded as the consequence of a chance intersection of succes- 

 sive meander sweeps on the valley side. But the dependence 

 of the sweeps, P and S', upon the defended spurs on the 

 northern side of the valley shows that the strong southern 

 cusp, Q, is not altogether accidental. It is in reality a natural, 

 although an indirect and temporary, product of the northern 

 ledges at M and K'. Unlike the defended northern spurs, 

 which are relatively permanent features, the indirectly de- 

 fended cusp, Q, will not endure. Its apex is already trun- 

 cated by a chance swing of the river against it ; it will be 

 more and more consumed as such swings are continued and 

 repeated. It is safe only so long as the river flows on curves 

 determined by the ledges at M. and K'. 



The truncated free cusp, W, on the south side of the valley, 

 is probably related to Brown's spur, F, in much the same 

 way that the truncated spur, Q, is related to Perry's spur, K^ 



Another southern cusp, T, is the remnant of a 15-foot ter- 

 race projecting far into the valley between the southern re- 

 entrants, T' and P. A strong scarp, T", with blunt salients 

 rises to the high plain back of T. The sharj) apex of the 

 cusp points directly to the ledges at M, yet it is entirely unde- 

 fended south of the river. It is probable that there was 

 something of up-valley carving on the eastern side of the 

 cusp ; a relatively unusual process, for, as has been stated 

 above, river meanders normally progress down-valley. But 

 in this case, the down-valley progress of a northern meander 

 was stopped by the ledge at M. The ledge probably acted as 

 a sort of fulcrum as soon as the river impinged upon it ; the 

 deeper the northern reentrant, X', was cut, the more nearly 

 the river must have turned square across the valley at M, and 

 the more it must have been turned against the down-valley side 

 of the spur, T. Something of the same kind probably occurred 

 when the reentrants, S', S", S"', were scoured out. 



