ELEMENTS IN SAND-PLAIN FORMATION 457 
conditions at the present time. Such observations have been 
made by Wright, Reid, and others in regard to the fine sedi- 
ments such as make up the so-called glacial clays, and it is upon 
these observations that the present estimates are based. 
Locality selected. —Conditions favorable to a calculation of 
the time of formation from the extent of the plains, or their 
associated clays, are in almost every case wanting. In 1896, 
however, Woodworth described? and mapped a series of unusu- 
ally typical deposits in the town of Barrington, R. I. A visit to 
the locality showed the conditions to be almost ideal, and 
admitting of calculations of some definiteness. The clays were 
selected as a basis of calculation in preference to the sand-plain 
itself, because of the greater number and reliability of the 
Alaskan observations upon this class of sediments. 
FGA 
Fic. 2.—Section across Barrington, R. I., showing relations of clays to sand- 
plains. A, Terrane of Carboniferous age; B, Glacial drift older than Nayatt Point 
stage; C, Clays contemporaneous with the Nayatt Point sand-plain; E, Gravel and 
sands deposited upon the melting of the ice along the head of the Nayatt Point plain ; 
F, Barrington sand-plain; G, Barrington clays; H, esker; I, gravel and sands laid 
down upon the melting of the ice back of the Barrington plain. —J. B. WoopWoRTH: 
Seventeenth Annual Report U.S. Geol. Surv., Part 1, p. 987. 
Barrington clays.—TVhese clays are exposed at the surface 
over an area of about six tenths of a square mile (Fig. 1). On 
the south the clays rest against the ice-contact slope of the 
Nyatt Point sand-plain, while on the north they extend as a 
gradually thinning wedge beneath the Barrington plain, reaching 
their northern limit approximately along the ice-contact slope of 
this latter plain (Fig. 2). The depth of the clays in the vicinity 
of the railroad, as shown by borings, is about sixty feet. With 
the exception of one slight break there is a ridge, partly till and 
Seventeenth Annual Report U.S. Geol. Surv., Part I, 987, 988; and Am. Geol., 
VoL. XVIII, 161-164, 391, 392. 
