THE SILURIAN BEACH. 
44 
along the Silurian beach ; let us return to gathei 
a few specimens there, and compare them with 
the more familiar ones of our own shores. I 
have said that the beach was a shelving one, and 
covered of course with shoal waters ; but as I 
have no desire to mislead my readers, or to pre- 
sent truths as generally accepted which are still 
subject to dispute, I would state here that the 
parallel ridges trending east to west across the 
State of New York, considered by some geolo- 
gists as the successive shores of a receding ocean, 
are believed by others to be the inequalities on 
the bottom of a shallow sea. Not only, however, 
does the general character of these successive 
terraces suggest the idea that they must have 
been shores, but the ripple-marks upon them are 
as distinct as upon any modern beach. The reg- 
ular rise and fall of the water is registered there 
in waving, undulating lines as clearly as on the 
sand-beaches of Newport or Nahant ; and we can 
see on any one of those ancient shores the track 
left by the waves as they rippled back at ebb of 
the tide thousands of centuries ago. One can 
often see where some obstacle interrupted the 
course of the water, causing it to break around 
it ; and such an indentation even retains the soft, 
muddy, plastic look that we observe on the pres- 
ent beaches, where the resistance made by any 
pebble or shell to the retreating wave has given 
