202 AGEL SLUR ALO 
The rock here consists of heavily bedded and remarkably pure 
Corniferous limestone which is being quarried for building pur- 
poses, road metal, and the manufacture of beet sugar and soda 
ash. Some thirty-five acres have been opened about which 
there is always to be seen a variable margin of glaciated surface 
from which the till has been stripped. A huge embossment of 
rock here represents the northern terminus of one of the rock 
ridges described previously. The rock surface dips in all 
directions from the crest, but less rapidly towards the south- 
west, so that conditions were most favorable here for receiving 
and recording the effects of any ice-sheet moving across this 
region from the west, north, or east. 
The marginal strip of rock surface, nearly a mile in length, 
shows pronounced glaciation by the late Wisconsin ice-sheet. 
The limestone has been planed down, striated, and gouged, and 
to a slight extent polished, but there are no furrows. The striz 
and gouges have a rather unique northwestward direction, forty- 
eight observations about the quarry giving an average of N. 
28.8° W. (true reading), with a range of 43° (N. 43.5° W. to N. 
o.5° W.). The general appearance of the rock surface, with its 
intersecting gouges, is shown in Fig. 3. ; 
The direction of ice movement is fully attested by a variety 
of phenomena, which were all clearly described by Chamberlin 
in 1888.t Strize are frequently found of the nature of the one 
shown in Fig. 3, beginning asa fine scratch, passing gradually 
into a gouge and ending abruptly toward the northwest, as the 
stone was suddenly crushed. Projecting masses of the bed rock 
were bruised and scratched upon the southeast side, while the 
northwest side is rough and unglaciated. ‘‘ Chatter-marks’’ are 
numerous with their convexities invariably turned toward the 
southeast and “plucking” is frequently to be seen upon the 
northwestern side of the elevated ledges. Previously formed 
furrows which have a northeast-southwest direction have their 
northwestern sides bruised and rounded, while the southeastern 
sides of these furrows meet the general rock surface with a well 
t Seventh Ann. Rept. U. S. Geol. Surv., p. 244. 
