54 J. D. Dana on Denudation in the Pacific. 
mulating beaches that protect it from wear. If this is the case 
on shores where there are deep bays, what should it be on sub- 
marine slopes successively becoming the shores, in which the 
surface is quite even compared with the present outline of the 
islands? Instead of making bays and channels, it can only give : 
greater regularity to the line of coast. | 
Upon the North American coast, from Long Island to Florida . 
there are no valleys in progress from the action of the sea. On 
the contrary, we ascertain by soundings that the bottom is singu- 
larly even; and the bays, as that of New York, are so acted upon 
| 
valleys. The valleys of the land are often two thousand feet | 
deep; but they die out towards the shores. Thus over the 
world, scarcely an instance can be pointed out of valley making" 
_ from the action of the sea. During the slow rise of a country, the 
» condition would not be more favorable for this effect than in a time 
“of perfect quiet. If America were to be elevated, would the action 
make valleys in the shores just referred to? If England were 
slowly to rise, would this favor the scooping of valleys through 
its beaches? Would not beach formations continue to be the legit- 
imate production of the sea along its line of wave action; a 
where the rocks should favor the opening of a deep cove, would 
not the same action go on as now, causing a wear of the head- 
lands and a filling up of the cove at its head?) Were Tahiti now 
to continue rising, could the waves make valleys on the coast? 
The increasing height of the mountains would give the streains 
of the land greater eroding force, aud more copious waters ; but 
the levelling waves would continue to act as at the present time. 
The effects of the sea in making valleys have been much exag- 
gerated, as is obvious from this appeal to existing operations, the 
appropriate test of truth in geology. 
‘The action of a rush of waters in a few great waves over the 
land, such as might attend a convulsive elevation, though gen- 
erally having a levelling effect, might produce some excavations, 
as is readily conceived; yet it is obvious on a moment’s consider- 
ation, that such waves could not make the deep valleys, miles 
in length, that intersect the rocks and mountains of our globe. 
Bat it is supposed that there may be fissures about volcanic 
islands in which the sea could ply its force. Yet even in these 
cases, unless the fissures were large, the seashore accumulations 
would be most likely to fill and obstruct them. ‘To try this 
hypothesis by facts, we remark that there are no such shore fissures 
around Mount Loa, nor any of the other Hawaiian Islands. The 
fissures formed by volcanic action immediately about a volcano, 
are generally filled at once with lavas as we have stated, and the 
a 
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