iSqs.J 
487 
[Davis. 
sand and gravel would require an amount of denudation and 
transportation since the glacial epoch — for the whole plateau, 
it must be remembered, has certainly not been overridden by the 
i ce — that is entirely inconsistent with what has been measured else- 
where. In the second place, as the plateau has a delta front, 
indicated both by its form and by its structure, it implies a standing 
body of water whether its materials were brought into that water 
body by river currents or marine currents ; and the existence of an 
open water level at the height of the plateau surface, or about a hun- 
dred feet above present sea-level, long enough for the building of 
so extensive a delta as would be required to stretch across the 
Charles River lowlands at Auburndale, is not consistent with the 
absence in other localities of a well-marked shore line at the same 
elevation. In the third place, the requirement of the original 
extension of the plateau across the lowland and the subsequent 
excavation of the lowland after the plateau was built, is incon- 
sistent with the form of the head of the plateau. A little north- 
west of the “big signboard” near Newton Lower Falls, there is a 
series of gravel mounds or kames and kettles along the head of 
the plateau, whose form is so manifestly of constructional and 
not of erosive origin that no one can believe that the plateau 
ever had any appreciable extension over them. They mark its 
original limit. Moreover, in the case of the larger plateau, which 
lies just east of Newton Lower Falls, there is a considerable 
marshy area on its northern slope, not open like a valley, but 
enclosed by drift hills on all sides, although recently artificially 
drained for purposes of cultivation. Like the kettles among 
the kames, this marshy depression forbids the extension of the 
plateau across the lowland, and confirms the conclusion that its 
original margin coincided practically with the present margin. 
It may be added that the interpretation of the head of the plateau 
as an original constructional form is confirmed by discovering a 
form of quite another kind on the western slope of the plateau, a 
quarter of a mile southeast of Newton Lower Falls ; here is 
a long concave margin, unmistakably produced by a swing or 
meander of the Charles River, before its channel had been 
sunk so low in the valley gravels as it now lies. This smoothly 
curved excavation in the side of the plateau is of especial value 
in illustrating Low clearly the marks of erosion on the plateau 
may be recognized, and hence in confirming the conclusion. 
