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Shaler.} | 280 [May 7, 
material stored in the coast fringes of our ocean shores, — movements 
brought about by the changes in the level of the lands. 
It is quite certain that the method of formation which we see 
now in the detrital shelves of our shores is the usual way in 
_ which the coarser detritus of geological formations is accumulated —- 
all our sands and gravels, as well as the larger part of the coarser 
muds, are necessarily laid down close to the shore line within the 
range of currents strong enough to carry them, so that the first place 
of deposition of the mechanical sediments is in this coast shelf — 
their further history depends upon the changes of position in the region 
where they are deposited. 
If any shore line along which a detrital shelf has accumulated is 
subjected to a rapid subsidence, the deposit will be buried beneath 
strata of another character. It will then, on subsequent elevation, 
appear to us as a strip of coarse, irregularly disposed sediments thin- 
ning out towards either edge, and having its greatest extension in 
the trend of the old shore line. The direction of the ancient shore 
will be indicated by the position of the coarser materials, which will 
generally prevail on the shoreward side of the mass. If, on the other 
hand, the shore line rises with considerable rapidity, the detrital mass 
will be worn on its landward, and rapidly accumulated on its seaward, 
border. Generally, however, the wearing action of the sea is not 
sufficient to take away the whole of the detrital mass with it in its 
retreat; a part remains, and is elevated above the water level. Thus 
the result of elevation is to disperse the matter composing the detri- 
tal shelf over a wide surface. 
I am inclined to believe that many of the sudden invasions of coarse 
sediments into what had hitherto been areas of pretty deep sea, may 
be accounted for by supposing that a process of elevation had brought 
about the removal seaward of great masses of detritus which, during 
the periods of greater stability, had been accumulating along the 
neighboring shores. My attention was first called to the questions 
. discussed in this paper, by the difficulty of accounting for the rapid 
deposition, and peculiar distribution of the carboniferous conglomer- 
ate or millstone grit within the Commonwealth of Kentucky. There 
we have a deposit of detrital matter of this age, accumulated with 
very great rapidity, having a thickness at some points of more than 
fifteen hundred feet, and showing throughout evidence of the action 
