(34(3 DR HUGH ROBERT MILL ON THE 



artificial, more than 32,000,000 cubic yards of material having been excavated, and 

 deposited mainly at the mouth of the estuary in Dunoon Basin, during the last fifty years. 

 The mean low water depth of the estuary is 5 fathoms, and the volume of water it 

 contains 0*11 cubic sea miles ; but the entrance of 0*03 cubic sea mile additional at high 

 water increases the mean depth to 6^ fathoms. 



The River Clyde, although a tidal canal from Bowling to Glasgow, has a great 

 drainage area, extending mainly to the east and south. With its tributaries it drains a 

 surface of 1140 square miles, which is not taken into account in discussing the drainage 

 area of the estuary. The Clyde drainage area is thus nearly one-third of the whole, and 

 is equal to the entire water surface under consideration. The upland course of the river 

 and its tributaries lies in a drier region than any of the other affluents of the Sea Area — 

 a fact which largely neutralises the effect of its great catchment basin. 



The name Gareloch I restrict to the part of the inlet lying north and west of Row 

 Point, and measuring 4£ square miles. Row Point is a sandy spit on the east shore, which 

 narrows the entrance to the loch to 300 yards, and is continued across the mouth by a 

 bar with less than 5 fathoms on it at low water. This bar separates the deeper water of 

 the loch from a narrow depression a little more than 1 fathoms deep, which runs in from 

 the Dunoon Basin. The Gareloch is 5 miles lono- and averages rather less than 1 mile in 

 breadth. It runs N.N.W. to within a mile of Loch Long, from which it is separated by 

 land under 500 feet in elevation. It is more open to the estuary than to the Dunoon 

 Basin, and on account of its shallow and narrow entrance the tidal currents are very strong. 

 The profile of the Gareloch is shown in section 17, Plate IX. The land surrounding it 

 rises with a gentle slope and is well wooded ; its height is slight, and only a few very 

 small burns trickle into the loch. Along the centre its depth averages 18 fathoms, and 

 the bottom is in all parts thickly covered by sewage-laden mud, carried in by the tides 

 from the estuary. The land drainage area to this loch is 12^ square miles, the low water 

 volume 0*024 cubic sea miles, with an average depth of 7\ fathoms, raised to 9 fathoms 

 at high water, when 0'005 cubic sea mile more water is present. 



Loch Long (Upper Loch Long) is a continuation of the Dunoon Basin, and 

 separated by a bar which rises to about 18 fathoms from the surface (section 6, Plate VII.). 

 It is remarkably straight, running N.N.E. by E. for 8-^ miles, and preserves a nearly 

 uniform breadth of half a mile all the way. The greatest depth, 35 fathoms, occurs 

 4 miles from the bar, or about half way up. The head of this loch is greatly shallowed 

 on account of the detritus carried in by a small river ; and at intervals along the coast 

 the innumerable torrents which foam down after a shower have formed a narrow beach. 

 The shore on both sides is mountainous and the slopes steep, the contour line of 1000 

 feet approaching within half a mile of the water's edge, and some summits exceeding 

 2000 feet. The superficial area is about 4 square miles, and the area of land drainage 

 29 square miles. The low water volume is about 0*033 cubic sea mile, with an average 

 depth of 24 fathoms along the axis, and 10 fathoms over all. At high water a rise of 1^ 

 fathoms is produced by the addition of 0*005 cubic sea mile of additional water. 



