G. H. Stone — Glacial Sediments of Maine. 139 



According to the above stated hypothesis the reticulated 

 kames neither connected with the deltas nor with those local 

 plains that were deposited in small lakes or pools where the 

 glacial streams were partly stopped, were formed in channels 

 within the ice, while in the delta plexus the reticulated ridges 

 were foimed in front of the ice, so that the gravel collected 

 in the stiller water at the sides of the swift current. 



It is probable that a large part but not all the reticulating 

 ice-channels were sub-glacial. 



Some additional considerations relating to the origin of the 

 reticulated ridges are the following : 



1. In the case of the deposits here termed deltas, we have a 

 gradual change of sediments from coarser to finer. This is 

 proof of a gradual slowing of swift waters, such as must hap- 

 pen when a rapid stream flows into a large body of rather still 

 water. But in the case of the plains of reticulated ridges 

 found above 230 feet, we can follow them for several or many 

 miles and find but very little sign of horizontal assortment of 

 sediments. The largest deltas below 230 feet show a decided 

 change in fineness within two or three miles. 



2. Wherever we find the horizontal gradation from coarser 

 to finer sediment, we also find in going in the same direction 

 the ridges growing broader (somewhat in fan-shape) and the 

 lateral slopes more gentle till the ridges coalesce in a rolling- 

 plain. But many of the osars fork into two or more branches 

 which continue of nearly uniform size for two or three miles 

 till they unite again. 



3. Take the case last cited of long diverging branches en- 

 closing a space one-fourth mile wide. If the space between 

 the branches was open water, how can we account for the pro- 

 digious size and swiftness of the stream which swept so wide 

 and long a space clear of sediments and left a ridge on each 

 side of it, yet permitted the deposit of a single ridge both to 

 the north and south of the double-ridge ? In such a case it 

 seems to me impossible that the space enclosed between the 

 ridges was kept clear of sediment by flowing water. The ar- 

 gument seems to be overwhelming that it was occupied by ice. 



There seems to be no other way to account for all the facts 

 except on the hypothesis that there were two classes of reticu- 

 lated ridges, one formed in branching ice-channels, the other 

 in open water where swift streams flowed into it. 



10. Osar Border-days. — In several places a kame or osar 

 is bordered on each side by a plain of grayish clay which in 

 some cases rises in a steep bank above the adjoining ground in 

 places where we can admit no recent erosion sufficient to 

 account for such a terrace. So, too, such clay plains are 

 found going over hills where no surface stream can have 



