EL. Andrews—Glacial Markings of unusual forms. 101 
were upon this rock some curves which were evidently deflec- 
tions caused by knobs and bosses on its surface, as for instance 
at Z. While other markings were erratic and curved without 
obvious cause, as though the ice had been swayed by swirling 
currents as the waters moved about it. The most of the glaci- 
ation was in the direction shown by the horizontal lines. The 
curved lines in the figure were selected from hundreds of 
others on a surface of about two rods square. They were gen- 
ane short, and some of the curves were of less than one foot 
radius. 
SERRATED STRL#. 
Behind the Cloche Mountains the Spanish River runs west- 
ward into Lake Huron. A branch of this stream, called the 
Sable, coming down from the hills on the north, presents near 
its mouth five cataracts within a distance of eight miles. At 
the lowest of the falls the river runs through a sort of rock 
flume, having upon both sides walls about forty feet in height, 
not quite vertical but with a slight inclination away from the 
Stream. ‘These cliffs are smooth and striated in every part par- 
allel to the stream. At the falls, which 
are only a few feet in height, the striz on 
curve with the descent, and also later- A 
ally with a bend of the cliff. On the /\/\/\A/\WA\ 
Walls of the gorge are to be seen a B 
few examples of the marks A and B, — amwsesm< 
Fig. 4 and the mark A is serrated, . 
the serrations being perhaps twelve ~~“ Cc 
inches high. Tt is not easy to explain >R_P PPP 
the cause of these strie in a perfectly 
Satisfactory manner, but it would seem that ice must have been 
driven through the flume with a rocking motion so that the 
widers on its lateral margins were cau to take a zigzag 
course, scoring the walls in a corresponding form, In B, fig. 4, 
