“wind gap” at this point cutting through the fold. At the 
southern end of this cirque now flows a tiny stream. Beyond 
its northern end, at the foot of the cliffs the Birse starts out of 
an opening in the limestone, with sufficient volume at its source 
to turn a good-sized saw-mill. The Suxe does not run along 
the bottom of a synclinal valley below the Fabrique d’ebauches 
south of Sonceboz, but cuts across the southwest corner of a sub- 
sidiary fold branching off from the Monto fold. A similar sub- 
sidiary fold seems to exist at the southern end of the Tavannes 
cirque forming its southeastern wall beyond the point where 
the north and south road traversing the cirque makes a strong 
bend to the southwest. Owing to this subsidiary fold the strata 
seem to be broken up at the southern end of the cirque , so that 
a crack might be predicated here ; for the strata on the west 
side, from an east and west course, with steep southerly dip, take a 
course slightly north of east on entering the gorge leading to the 
cirque. The strata near the 703.53 meter level in the road, have 
a north-northwest strike with the dip southwest. However, on 
the cliffs south and southeast of the 763.39 meter level in the 
road, the strike is more decidedly east-northeast than on the 
opposite side of the gorge leading to the cirque , but the dip is ap- 
parently 70 degrees to the north. A little further north on this 
east side of the valley, but in the cirque proper, the strata had 
a low southern dip, perhaps 20 degrees, the dip increasing south- 
ward. Corresponding facts were not noticed on the west side 
of the gorge. The facts may warrant the existence of a break 
here, at the southern end of the gorge, but they seemed to me 
to suggest rather the existence of a fold, similar to that directly 
southeast of Sonceboz, which can be more readily detected. 
The main body of the cirque shows no evidence of faulting ; 
unfortunately exposures on either side are so far distant from 
each other as to make correlation difficult. At the northern end 
of the cirque , however, it is not only certain that there never 
was a fault but equally certain that there never was a gaping 
crack, because a wall of strata here extends across the valley 
and thence up the mountain side without the evidence of a 
break of any kind. This wall, jnerced by the Roman emperor 
in order to reduce the grade of the military road traversing this 
cirque , is still intact above and forms an arch over the road, and 
is known as the Pierre Pertuis. It alone should be sufficient to 
