MEDINA SANDSTONE. 
55 
The woodcut No. 11 is an illustration of these lines as they appear upon a slab about 
five feet in length. The course varies but little in the numerous instances which I have 
examined. A line perpendicular to the curve generally gives a direction differing but little 
from N.N.W. and S.S.E.; which shows that the direction of the wind varied between north¬ 
west and north, and that the line of beach must have been nearly at right angles with this 
direction, which corresponds very generally with the present line of outcrop of this rock. 
Existing phenomena of the character here described may be witnessed every day upon the 
shores of the ocean, or of the larger lakes. Any one who has passed along a sandy beach 
during the ebbing of the tide, or when toward evening the fresh breeze of the day is lulling, 
must have observed as the waves roll in and extend far up in a thin sheet of water, that the 
crest of each one forces on before it a film of sand. This, when it has arrived at its extreme 
limit, and during the moment which elapses between its advancing and retreating motion, is 
deposited in the form of a minute ridge or line, defining perfectly the outline of the wave. 
These occur one after the other, sometimes crossing and sometimes parallel, but always 
marking the limit of the water. Often after many of these are formed, a wave advancing 
beyond the others, obliterates the whole, and leaves its own line far above them ; and if its out¬ 
line do not correspond with the previous ones, those portions of the former lines are left limited 
by the last. When the beach dries rapidly from the heat of the sun, these are distinctly seen, 
preserving most perfectly the outline of the wave in all its minute curvings and undulations. 
So minute are the ridges, and the amount of matter so small, that a gentle wind is sufficient 
to remove the whole, and it might seem almost fanciful to suppose that any vestiges of them 
are preserved; yet after having made repeated observations upon these wave lines, and upon 
the markings on the strata in the quarries at Lockport, I was forced to the conclusion that the 
cause of both was identical. During the past summer I examined these quarries, and also 
the recent operation upon the sandy beaches of Lakes Ontario and Erie, in company with 
Mr. Lyell, and I now have the pleasure of recording his opinion as coinciding with what has 
been expressed; namely, that the cause producing the markings upon the sandstone is iden¬ 
tical with that producing wave lines upon our present beaches. 
In several places west of the Genesee river, on the shore of Lake Ontario, are large bays 
or ponds, separated from the lake only by a sandy beach, and usually having a narrow outlet, 
or sometimes none at all, for a considerable time, until the accumulation of water inside forces 
a passage through the sand. At one of these places, there was a broad flat beach, rising 
but little above the level of the lake, and sloping gently back to the marshy margin of the 
pond. A previous high wind had raised the lake, and the heavy waves had washed entirely 
across this beach into the pond. The surface beyond the highest point where the water flowed 
smoothly down, was covered with pebbles, some fragments of shells, and the bones and scales 
of fishes. Every one of these had offered some obstruction to the advancing water ; and in 
that direction, and on each side, there was a depression or shallow excavation, while beyond 
the obstacle extended a little ridge of sand narrowing and sloping down to the general surface. 
