Davis. J 
484 
[May 1 8, 
and stones of which the ridges are chiefly composed were some- 
times washed up-hill along a moderate slope, as the northern end 
of the shorter eskers is often lower than their southern end. If 
formed on the ice, it is difficult to understand how their simplic- 
ity of linear form could be preserved ; for as the ice melted away 
on either side and underneath they would be more likely to slide 
off to one side or the other in irregular deposits than to remain 
in simple linear form. 
I believe that it is possible to discriminate in some cases be- 
tween these rival suggestions ; but it is not intended to overdraw 
conclusions and state that all eskers must be formed in the same 
way as were those that have come under my observation. The 
method or argument leading to the adopted conclusion in the 
cases studied consists essentially in a parallel development of 
observation and generalization ; until at last the correlated facts 
demand so specialized and complicated an explanation that only 
one theory can in any probability supply it. 
6. THE AUBURNDALE DISTRICT. 
During the construction of the circuit line of the Boston and 
Albany Railroad, a deep cut was made in a little plateau of 
gravel and sand between the stations of Woodland and Waban, 
about a mile south of Auburndale. A little further west a cut 
was made through a sharp-ridged esker, exposing its loose stony 
structure. A few years before, extensive excavations had been 
made in a neighboring sand plateau towards Newton Lower Falls 
to gain material for filling in the Boston Back Bay. All these 
artificial sections, combining with a strongly expressed topo- 
graphy, give the Auburndale district a high value in the study of 
glacial geology. 
7 . THE SAND PLATEAUS. 
The deposits of the district are easily divided into three series 
as indicated both by form and structure. These are the sand 
plateaus 1 , the gravel ridges or eskers, and the sand mounds or 
I have previously called these “ sand-plains” in an essay published in the Bulletin 
of the Geological society of America, but am now tempted to follow a suggestion of 
Mr. Upham and name them “sand plateaus” in order to give emphasis to their ele- 
vation above the adjacent meadows. 
