G. H. Stone — Glacial Sediments of Maine. 131 



ends of the longer systems, the ridges have an uneven surface 

 and steep lateral slopes like some moraines. The material is 

 barely water-worn. It is till with the finest detritus washed 

 out of it, and the stones have been left, but little changed from 

 their till shapes. As we go southward the stones become very 

 much worn and rounded. The facts are only to be accounted 

 for as due to glacial rivers flowing southward in narrow chan- 

 nels bordered by ice walls. Rising out of the rather level 

 regions of central and eastern Maine to a height of 20 to 150 

 feet above the adjacent land, these long embankments form a 

 remarkable geological construction. They freely pass over 

 hills of moderate height from one drainage basin to another 

 and they cross rivers and lakes. The ridges are seldom con- 

 tinuous for more than ten miles, because they are usually in- 

 terrupted near the tops of hills crossed by the systems, also on 

 clown or southward slopes of thirty or more feet per mile. 

 Here there appear to be topographical causes for such swift 

 currents as would sweep the ice-channels clear of sediment. 

 At the contour of 230 feet or not far south of it, they become 

 regularly non-continuous, even when traversing quite level 

 plains where there is no apparent topographical reason for the 

 interruption. At first the unconnected ridges are a mile or 

 two long and the gaps between them are short. By degrees 

 the system passes into a series of lenticular kames separated 

 by intervals many times as long as the kames themselves (up 

 to a mile or more). This gradual passage of a nearly continu- 

 ous ridge into a series of far-separated heaps furnishes part of 

 the argument for regarding a non-continuous kame system, so- 

 called, as having been deposited by a single glacial river, but a 

 short one. If it had extended north farther into the interior, 

 a continuous ridge would t probably have been formed in the 

 northern portion of its channel. 



Most of the osars expand into one or more marine deltas. 

 When there are more than one, they are situated ten to 

 twenty-five miles apart, and the largest one is in most cases, 

 the one farthest north and nearest the contour of 230 feet. 

 Some of them contain ten or even twenty square miles. 



Marine deltas of glacial sediments are of at least two well 

 defined classes. 



1. Fan-shaped Deltas. — In this class, as we pass from the 

 area where the reticulated ridges are highest and enclose the 

 deepest kettle-holes, we find the coarser sediments becoming 

 finer in all directions both in front and laterally. Here evi- 

 dently one or more glacial rivers flowed into the open sea, 

 where they were free to spread outward through a semicircle. 

 Going outward we find the gravels becoming sands and the 

 sands become finer and at last pass into the marine clays. 



