Beach Structure in Medina Sandstone. — Fairchild. 13. 
At points where shoreline topography or streams produce 
diversion or conflict of currents the emhankments may He in 
different directions and may even enclose basins. Figure 15,. 
plate VI, show such a basin at the outlet of Irondequoit, and 
figure 14 shows a similar basin in the ^Medina, where basining 
dip is not infrequent. 
Argument against "giant ripples." 
1. For troughs 30 feet across Mr. Gilbert suggests waves 
of the Medina sea 60 feet Jiigh. But the highest waves of the 
Atlantic are, according to Scoresby, only 43 feet high. On 
the other hand, the writer has seen troughs in the Medina 
sandrock up to even 80 feet across. 
2. If these ridges were deep-water ripples then we should 
expect to find ripples of all lesser sizes down to the common 
form. Can any geologist report true ripples broader than 
three or four inches? 
3. If these ridge-and-trough structures were deep-water 
phenomena then they should be common features in all deeper 
water deposits, as shales and limestones. Figure 6, plate III, 
shows a section in the old Whitmore quarry, north of Lock- 
port. The absence of curving structure in the shale is appar- 
ent, while a large concavity, 40 feet across, lies in the heavy 
bottom stratum of sandrock. This sand stratum is the same 
horizon as the one containing Mr. Gilbert's ridges, shown in 
figures 7, 8 and 9, and is about 60 rods westward. 
As "giant ripples" these ridges should occur in series or 
succession of uniform direction, hight and spacing. On the 
contrary they are usually isolated and single and in the same 
quarry lie in different directions. The nearest approach to a 
series of crested ridges that has been found is shown in figure 
2, ])late II. It will be seen that the ridges in this view are 
of diminishing size toward the right, while the larger ones at 
the left are rounded and without crests. These characters- 
agree precisely with those found on the modern beach. It is 
only a series of diminishing size that can be formed, since a 
stronger storm necessary to make the larger ridge would cause- 
the waves to override the previous smaller ridges and destroy 
them. The older ridge, exposed to the air and drying, soon 
loses its crest, if it had one, and assumes the rounded form 
seen in figure 2, plate IT. and in figure 10, plate V. 
