NIAGARA FALLS. 
397 
189. 
а. The terrace with shells on the eastern side. c. The terrace on the Canada side. L. Limestone. 
б. Goat island. d. The ancient drift. S. Shale. 
From the present position of the remains of this deposit, there can be no doubt but it was 
once continuous, the greater part of it having subsequently been removed. The mode of its 
formation can be well illustrated by referring to fig. 186, a, a, which is intended to represent 
what is now going on in the broad expansion of the river above the rapids. This fluviatile 
deposit is made by materials brought down by the current, and doubtless mingled with a 
large accumulation of shells of Unio, Melania, Anculotus, &c. as these shells are abundant 
above the falls, and large numbers of the shells of Uniones are constantly brought down the 
rapids during the summer season. 
The single terrace containing shells is not the only one ; on the eastern side, at lower eleva¬ 
tions, there are in succession three others (as seen by the acompanying topographical map of 
the falls), which seem to be remains of the deposit in the river bed, as it successively exca¬ 
vated its barrier on the north, and receded towards its present position. For the greater part 
of the distance from the falls to Black-Rock, on the eastern side there is a terrace or bank a 
few feet higher than the river, which may have originally limited its waters when it stood at 
the level indicated by the freshwater deposit of Goat island. Near Black-Rock, and border¬ 
ing the valley of the Tonawanda, there is a terrace some twenty feet higher, which appears 
to have been the boundary of the river or lake at a still earlier period; but with these we 
have, at present, nothing to do. The existence of the fluviatile deposit of Goat island, and at 
the same level on the eastern side of the river, requires for its elucidation the existence of 
water standing at a level somewhat higher, in order to allow of the deposit being made in the 
bed of the stream. To accomplish this, a barrier is required further north than the Whirlpool, 
and about the height of the surface of limestone between this and Lewiston. The occurrence 
of successive terraces below this one, proves that the drainage to the present point was not 
effected suddenly. 
There is another fact which should be noticed, as proving the existence of a current from 
south to north, during the deposition of the materials forming Goat island. The pebbles, at 
least large numbers of them, are of the limestone of Black-Rock, and the harder layers of the 
Onondaga salt group, like the rock in place at the upper end of Grand island. The surface of 
the rock, on which the deposit forming Goat island is made, is smoothed and scratched, as 
