24 
MUSEUM BULLETIN NO. 25. 
seen on the seashore. Since ripple-mark is not uncovered on the 
lake shore as it is twice daily on the seashore by the ebbing tide, 
its almost universal occurrence on suitable bottom a few feet 
or yards from shore in water of moderate depth might never be 
suspected by the casual observer. Observations made from the 
lake shore alone, however, would lead to the erroneous con- 
clusion that ripple-mark is not widely or generally present on 
sandy bottom; for it is developed in water very near the 
shore-line only where the slope of the bottom is very gentle. Where 
the shore slopes abruptly under the water ripple-mark is not 
formed up to the very edge of the beach. A 2-mile walk for 
example along the sandy beach of lake Ontario near Wellington 
when the waves are forming ripple-mark would enable one to 
see ripple-mark along perhaps not more than 100 yards of this 
distance (Plates XX and XXI). But observations made from a 
small boat off this shore in water 4 to 10 feet deep would show an 
uninterrupted stretch of ripple-marked bottom. A water glass or a 
small wooden box with glass bottom will enable the observer, where 
the water is clear, to see the wide distribution of wave ripple-mark 
wherever the bottom is sandy. One of the localities on the , 
Ontario beach, where the slope is sufficiently gentle to permit 
ripple-mark formation nearly to the edge of the water, is rep- 
resented in Plate XX A and B, which shows ripple-mark through 
a very thin cover of water and the advancing waves which have 
formed it. 
Under the conditions generally met with along sandy lake 
beaches, a broad belt of smooth sand is seen which extends from 
the upper limit of wave action under the water. The swish of 
the water from advancing and retreating waves across this zone, 
varying from a few feet to many yards in width, which is alternately 
submerged and uncovered does not form ripple-mark. But it 
leaves a very distinctive and characteristic record of wave action 
under subaerial conditions in the shape of fine thread-like 
ridges of sand called wave-marks which mark the maximum reach 
of the waves at any particular time. The appearance of these 
is indicated in Plate XIX A. The front of the nearly exhausted 
wave which makes them is shown in Plate XVIII. The remnant 
