SYSTEMS OF DISCONTINUOUS OSARS, 377 



osai's there can be no doubt of the action of a single glacial river, even 

 when the ridge becomes interrupted. The feature of noncontinuity can 

 not, therefore, in itself be urged as 2Droving the action of more than a single 

 stream. Genetic connection is to be proved or disproved by general con- 

 siderations, the nature of which has been referred to elsewhere. 



The feature of systematic noncontinuity is almost wholly confined to 

 the coast region. The longer osars and osar-plains frequently extend 10 to 

 30 miles south of the contour of 230 feet before they become discontinuous, 

 but the discontinuous character rarely extends north of that contour, and 

 then usually in a modified form ap^jroaching the osar type (e. g., at North 

 Monmouth). 



In the noncontinuous systems the gravel deposits are from a few feet 

 up to 3 miles long, and they are separated by intervals varying within the 

 same limits. The intervals between the successive deposits are a constant 

 and distinguishing feature of the class. The intervals are due to the original 

 manner of deposition. Ridges formed by the unequal erosion of a contin- 

 uous plain are not entitled to the same name as ridges that were oi'iginally 

 formed in substantially the same shapes they have at present. For this 

 reason the terms "kame" or "osar" are not in this report applied to ridges 

 consisting of portions of the valley drift or other alluvial plains which have 

 been left as ridges simjjly because the surrounding matter has been eroded. 

 The gravel masses under discussion have sometimes been eroded, but the 

 erosion can readily be traced, and it can be asserted with greatest confi- 

 dence that no continuous mass of gravel ever connected them. This is 

 the more certain because they are mostly situated in the region that was 

 under the sea and the gravels are wholly or partly covered by marine clay, 

 which would protect them from erosion. Any agency which would erode 

 the gravels must first erode the overlying clay. But in most places the 

 clay still remains or has only partially been eroded. In some cases ridges 

 which appear to be discontinuous may really be connected by a low ridge 

 now covered from sight by the clay. But in many places streams flow 

 across the space between the apparently separate deposits of the same 

 system, and in their banks no gravels are seen, though they cut down to the 

 till or even to the underlying rock. 



Any satisfactory explanation of the discontinuous osars must account 

 not only for the deposition of the gravels but also for the intervals between 



