of Edinburgh , Session 1884 - 85 . 47 
ends and the firth begins being a matter permitting of difference of 
opinion. Probably the best plan is to view the river as ending at 
Queensferry, but for convenience the term Firth of Forth may he 
applied as describing the river and firth proper from Alloa to the 
Isle of May, a distance of 55 miles. According to Keith Johnston, 
the area drained by the Forth is 500 square miles. Few large 
rivers flow into the firth, those of any importance are, on the north 
side the Black Devon at Clackmannan, and the Leven at Leven ; on 
the south side there are the Carron at Grangemouth, the Avon a 
few miles further east, the Almond at Cramond, the Water of Leith 
at Leith, the Esk at Musselburgh, and the Tyne near Dunbar. All 
these, together with the numerous small burns, are represented 
on the chart (Plate III.), which also shows the depth of the water in 
the firth. 
From Alloa the depth of the water is under 10 fathoms until 
within three miles of Queensferry, where it increases at first 
gradually, then, at the Bamer Beacon, abruptly to over 30 fathoms, 
and close to Iuchgarvie to over 40. This is the deepest part of the 
firth, and the narrowest. A very strong tide runs in the channels 
on each side of Inchgarvie. The deep water is confined to a small 
area, and the 10 fathom stream runs along the northern shore 
until off Kirkcaldy, where it widens out in a funnel shape and 
approaches the coast on each side. There is a short tract over 10 
fathoms to the south of Inchkeith known as the Narrow Deep. 
Several small depressions of more than 20 fathoms occur between 
Queensferry and Inchkeith, and a little to the east of that island 
the 20 fathom area begins as a narrow stream trending northward 
and spreading out off Largo. The Isle of May is connected to the 
mainland of Fife by a submerged plateau rising to less than 20 
fathoms from the surface, and about 4 miles east of the May 
depths beyond 30 fathoms commence. 
A line drawn from Aberlady Bay to Largo divides the firth 
into two very different halves. To the west of it, the slope of the 
bed is extremely gradual and the depth slight ; to the east of it, the 
shore slopes down abruptly, and the bed of the firth is, with one or 
two insignificant exceptions, uniformly over 20 fathoms in depth. 
