220 
NATURAL BRIDGES OF UTAH 
\ 
more and more tortuous, often forming pronounced recesses be¬ 
neath overhanging cliffs, that resembled huge sounding-boards 
built for out-of-door entertainments. Ideal conditions were fur¬ 
nished for the formation of a bridge when two of these recesses 
were produced, one on each side of a narrow neck (PL xii.). 
By reference to figure 17 it will be noted that White Canyon 
formerly made a sharp meander just before reaching Armstrong 
Canyon and approached the latter, somewhat abnormally, at an 
up-stream angle. By the time the channels had entrenched them¬ 
selves to the depth of the argillaceous sandstone, the combined 
action of the two streams undercut the formation at the neck 
B, and permitted the water of White Canyon to flow under the 
bridge as indicated. The abandoned stream channel at the bend 
A is slightly less than 100 feet above the stream-bed at C. Nat¬ 
urally, its level is also approximately the same as that of the 
argillaceous sandstone. 
The conditions at the Augusta bridge are slightly different. 
By referring to figure 17c it will be seen that a tributary formerly 
entered White Canyon just! at the outward swing of a sharp 
meander. After the White Canyon stream had imbedded itself 
to the proper horizon, it worked its way beneath the narrow neck 
B in much the same manner as had been done at the other bridges. 
Just here, however, an unusual thing occurred. Prior to the time 
of the formation of the bridge, the White Canyon stream passed 
the point C in the direction indicated by the dotted arrow, but 
after the principal stream had deserted this section of its channel, 
the one coming in from the tributary reversed the former di¬ 
rection of flowage at C and now travels as shown by the full 
arrow. 
The conditions which produced the Edwin Bridge differ only 
in detail, rather than in principle, from those which produced 
the Carolyn Bridge. Again referring to figure 17a, it is noted 
that in the immediate vicinity of the Edwin Bridge the tributary 
formerly entered Armstrong Canyon at the point marked E, 
but later, because of meandering of both streams, it broke under 
the narrow neck — at the horizon of the argillaceous sandstone — 
and immediately deserted its channel at A. Thereafter it flowed 
under the bridge as indicated by the arrows at B. The abandoned 
part of the channel at A is now 50 feet higher than the stream- 
