LAKE PASSATG. 541 
of Chatham is an illustration. In the vicinity of Basking Ridge, 
deposits of trap gravel grade into those of shale where the shore 
line passed from the trap to the shale. Along the gneiss high- 
lands the two gravel beds known along the margin of the lake, 
are largely of gneissic gravel and sand, and local sources for the 
other constituents are at hand. Near New Vernon the gravel 
deposits on the trap hills are mainly of trap, those on the shale are 
composed chiefly of shale, while those on the Triassic ‘conglom- 
erate are of quartzite pebbles, derived from the conglomerate 
itself. The foreign pebbles in the shore gravels may belong (2) 
to the older drift, remnants of which occur at various points 
about the lake; or (0) they may have been transported along 
the shore of the lake from the newer drift; or (c) they may have 
been carried to the shore of the lake by blocks of floating ice, 
starting from the moraine. 
Waves and shore currents are the only known agencies which 
can develop water-worn, stratified gravel, sustaining this definite 
relationship to the adjacent and subjacent formations. The 
topographic situation of some of these shore deposits of gravel, 
taken in connection with their composition, is such as to admit 
of no second interpretation. Generally speaking, they occur 
along a horizontal belt at a definite elevation, either (z) on the 
slopes of higher lands, or (4) in the passes and cols between 
them. Above this definite level, gravel such as described does 
not occur. Below this level, such beds of gravel occur as might 
have been formed during the later stages of the lake’s history, 
when its level was sinking and its area diminishing. 
A careful study of the shore deposits, particularly their rela- 
tions to headlands of rock and wave-cut benches, gives us some 
knowledge of the general direction of the waves and shore cur- 
rents. On Long Hill the shore drift traveled, in general, south- 
westward, as shown by the terrace near Chatham, the spit west 
of New Providence, and the spit west of Berkeley station. Near 
Basking Ridge the material was carried southward, as shown by 
the shale gravel southwest of Moore’s hotel, and the trap gravel 
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