246 
NIAGARA. 
cataract will be increased by the addition of the fifty feet 
that the stream now falls in passing the upper rapids. The 
excavation of the new receding channel may not extend 
across the entire two miles width of the river, and may 
probably be limited to a central portion of greatest depth and 
force of current; in that case the American Fall on the 
opposite side of >at Island from the new excavated channel 
may be expected to be run dry, and to show only a bare 
precipice in place of the present cataract, and the “ Cave 
of the Winds,” though still a cave, would lose both its water 
and winds. When the cataract recedes still further to the 
point where the stream divides into two channels it will 
depend upon the force of current and the nature of the 
bottom in each whether the cataract recedes along both 
streams equally or not. 
The volume of water that is constantly rushing over the 
Niagara Falls has been estimated at about a million cubic feet 
per second, or about six million gallons per second. An idea of 
this quantity of water can be formed from the size of the Bir¬ 
mingham Town Hall; imagine the interior of the hall entirely 
cleared from galleries and orchestra, leaving the bare external 
walls, then this quantity of water would fill it from floor to 
ceiling twice over every second. Some idea of the probable 
correctness of the estimated discharge of a million cubic feet per 
second may be readily formed from the following general dimen¬ 
sions :—2100 feet width for the Horse-shoe Fall, 1100 feet width 
for the American ball, and 70 feet for the Centre Fall; and 
then taking twenty feet for the thickness of the stream of 
water at the Horse-slioe Fall, and assuming two-thirds that 
depth at the American Fall, and one-third at the Centre 
Fall, a total sectional area of about 60,000 square feet is 
obtained for the stream of water at the edge of the Falls ; 
then this area of stream with a velocity taken at twelve 
miles an hour, or eighteen feet per second, gives a discharge 
of about a million cubic feet per second. At the ferry below 
the foot of the Falls, where the depth of water is 180 feet, 
and the width about a quarter of a mile, the same quantity 
of water per second gives a current running at only about two 
and a half miles an hour, and slow enough to allow of being 
crossed by a small rowing boat. 
In an interesting paper on Niagara Falls which was given 
at the recent Montreal Meeting of the British Association, it 
was pointed out that the peculiar conditions that are present 
there, namely a hard stratum forming the upper part of the 
precipice over which the cataract falls, with a soft stratum 
forming the lower portion that is continually being caved out, 
