E. Desor on the Post-Pliocene of the Southern States. 55 
out New England and Canada. Geologists have proposed various 
solutions of this great problem. 'To examine them all would 
lead us far beyond our limits. 1 shall therefore merely allude to 
some of the theories, and point out the characteristic features of 
each. 
The most ancient theory, and at first sight the most simple, is 
that which ascribes the transportation of the boulders to a vio- 
lent action of the waters, progressing from north to south either 
in form of currents (according to Sefstro6m, von Buch, Elie 
Beaumont) or in form of earthquake waves (according to Profs. 
Rogers), such as are sometimes known to sweep over the islands 
of the Pacific and to cover them with debris. In each of these 
hypotheses it is assumed that the momentum of the current or 
earthquake wave went on decreasing gradually and that the limits 
of the boulders mark the place where its power of transportation 
became exhausted. This explanation appears indeed to be borne 
out in various localities of the interior of the country, as was 
pointed out by us elsewhere.* But there is this objection to its 
application to the littoral regions under consideration. It must be 
assumed, in accordance with the well known facts, that wher- 
€ver a transportation by water takes place, there is a constant re- 
lation between the size of the materials and the momentum of the 
transporting current or wave; the former decrease in size and 
Weight in proportion as the force by which they are impelled de- 
creases. Now such is not the case on Long Island, Martha’s 
Vineyard, Nantucket and along the coast of New Jersey. There 
the materials are generally finely comminuted and regularly strat- 
ified, indicating at the first glance that they have been deposited 
ma quiet manner. On the surface of these strata of fine sand 
We find the boulders scattered here and there, generally on the 
Prominent points, as for instance on the island of Nantucket, and 
generally as large if not larger than those farther north. In 
such cases, it is obvious that no theory depending on aqueous 
ha: 
ee eee en 
Daur Oster and Whitney's Report on the Geology of the Lake Superior Land 
