28 
MUSEUM BULLETIN NO. 25. 
current made ripple-marks consequently trend at right angles 
to the coast-line. Lake shore and sea shore ripple-mark are thus 
differently oriented with respect to their adjacent shore-lines, 
the former trending with the shore-line, the latter at right angles 
to it. 
The relationship which the amplitude of wave-made ripple- 
mark bears to depth is a subject which needs further investigation 
before any final conclusion can be formulated. Mrs. Hertha 
Ayrton 1 concludes as a result of experimental work on ripple- 
mark in small tanks: “But as the heights and ripple-distances 
of all vary with the amplitude of the wave, they are greater 
after a storm than during calm weather." My own observations 
on ripple-mark in water from 1 to 25 feet deep do not appear to 
sustain this opinion. Little if any change in the amplitude of 
ripple-mark was observed after periods of stormy weather. 
Mrs. Ayrton also states that the side of a ripple facing the shore 
is steeper 2 than the opposite side. None of the numerous wave 
ripple-mark moulds which I have taken under water, however, 
show any modification of symmetry with reference to the shore-, 
line. The precise relative influence which depth and wave 
amplitude have on the height and spacing of ripple-mark has 
not yet been ascertained, although the observations made 
indicate that depth is one of the factors controlling amplitude of 
ripple-mark. Observations in shallow water clearly show an 
increase in the size of the ripple-mark ridges and troughs with 
increasing depth; to what depth and at what rate this increase 
will extend remains to be determined. A large number of observ- 
ations on ripple-mark in water less than 6 inches deep indicate 
that the crests of the ripples at this depth are never more than 1 or 
2 inches apart. In water 3 to 10 feet deep the crests are from 2 \ 
to 5 inches apart. The following series of observations taken near 
Wellington in water ranging in depth from 15 inches to 20 feet 
will suffice to show one example of the evidence secured on this 
problem. 
1 Proc. Roy. Soc. Load. ser. A, vol. 84, 1911, p. 307. 
* Ibid, p. 305. 
