ORIGIN OF VALLEYS. 383 
is obvious on a moment’s consideration, that such waves could not 
make the deep valleys, miles in length, that intersect the rocks and 
mountains of our globe. 
But 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 vent is mended by the force which 
made it. It is, therefore, a gratuitous assumption that such fissures 
have been common. ‘The existence, however, of large valleys such 
as have been attributed above to convulsions cannot be doubted; but 
the sea would exert its power in such places, nearly as now in 
Fangaloa Bay, Tutuila, and other bays in continents;—a beach 
forms, and a shore plain, and afterwards there is little action from 
the sea in these confined areas of water. 
In the Illiwarra district, New South Wales, there are several places 
where dikes of basalt have been removed by the sea, and channels 
one hundred yards in length, of the width of the dike (six feet), now 
exist, cutting straight into the rocky land. ‘This is an example of the 
action of the sea where everything is most favourable for it. And 
we observe that there is little resemblance in this narrow channel 
with but a trifling wear of the inclosing rocks, to the valleys which 
are to be accounted for in the Pacific; and little authority to be 
derived from it for attributing much efficiency to the sea in wearing 
out valleys. The reason of this is apparent in the fact that the sea 
rolls up the coast in great swells, and cannot parcel itself off, and act 
like a set of gouges: this latter effect it leaves for the streams and 
streamlets of the shores, which are gouges of all dimensions. 
Although the sea can accomplish little along coasts towards exca- 
vating valleys, yet when the land is wholly submerged, or only the 
mountain summits peer out as islands, the great oceanic currents 
sweeping over the surface and through channels between the islands, 
would wear away the rocks or earth beneath. From the breadth 
and character of such marine sweepings, we learn that the excavations 
formed will be very broad rounded valleys; and their courses would 
correspond in some degree with the probable direction which the cur- 
rents of the ocean would have over the region in case of a submer- 
gence. The direction of the Gulf Stream and that of the North Polar 
