271
OF ENGINEERING FOBMULÆ.
Canals.
Ordinary Dimensions for
dimensions, special traffic in feet.
Depth of water 5 feet — D + 1*5 foot.
Width at surface 40 feet = 3 B 4 3 (D 4-1'54. ,
,, bottom 25 feet = 3 E.
LOCKS.
Clear width .. = B + 1 foot.
„ length .. = L + 1 foot.
Depth, minimum, = D + 1J foot. _
Where D = Maximum draught of boat in feet;
B = Extreme breadth of boat in feet;
L = Extreme length, of boat in feet, in-
cluding rudder.
Ordinary canal lock, 75 feet long, 8 feet broad,
5 feet depth over sill.
Loss of water in canal«, exclusive of water
expended in passing boats through locks
Let A = Total area of surface of canal in sq. yds.
L = Loss of water in cubic feet per day.
For England .. L = 1‘5A+ 15,000.
Cubic contents of lock, less the displacement,
equal the amount of water expended in passing a
boat through the lock. If boats be locked up and.
down alternately, half the water only will be used;
if double locks be used they will effect a saving of
half the water.
ORDINARY CANAL “ OVER BRIDGES.”
Width of waterway at surface of water 13 ft.
,, 5 feet below surface 11 „
Headway above surface ............11
Semicircular arch.................20 „ span«
Width of towing path........., ..6,.