650 DR HUGH ROBERT MILL ON THE 



becoming higher and steeper toward the head. This brae is broken by only three glens or 

 valleys, all short and steep, as the watershed runs within 2 miles of the margin of Loch 

 Fyne. The Glen at Strachur meets that of Loch Eck, the Glen at St Catherine's meets 

 Hell's Glen, w T hich drains to Loch Goil, and that of Ardkinglass, at a still greater elevation, 

 joins Glencroe, which descends to Loch Long. The summit levels at which the water- 

 sheds occur in these cross glens are respectively 173 feet, 720 feet, and 860 feet. Coach 

 roads traverse each, and these supply practically the only routes across the peninsula. 

 In strong contrast to this uniform margin, the north-west edge of the Dunoon Basin- 

 Loch Long hollow is deeply indented by the openings of numerous long glens, many of 

 them containing sea lochs, others slightly elevated above sea level, and all directed 

 toward Loch Fyne, cutting up the peninsula into a number of rudely ovoid mountain 

 masses, with their longer diameters north and south. The drainage area of the narrower 

 and smaller Dunoon-Loch Long Basins is thus very much greater than that of the wider 

 and larger Arran-Loch Fyne Basins. 



Tables and Statistics of Physical Geography. 



For purposes of calculation it is more convenient to employ the sea mile of 6000 feet, 

 or 1000 fathoms, as a unit of measurement than the statute mile of 5280 feet; the 

 former is also very nearly equal to 1' of latitude — an additional advantage, as the charts 

 from which many of the measurements are made are simply graduated into degrees and 

 minutes. Volumes and mean depths of sea basins are most easily calculated by using 

 the sea mile, since a square sea mile of water 1 fathom deep is O'OOl cubic sea mile ; and 

 the volume of a basin in cubic sea miles, divided by the superficial area in square sea 

 miles, gives the mean depth in fathoms by shifting the decimal point. In all cases, 

 except the statement of volumes, the measurements were original^ made in statute 

 miles, and translated, when necessary, into other units. The land maps of the Ordnance 

 Survey and the reduced Ordnance maps of Mr Bartholomew, on wdiich the drainage areas 

 were measured, are supplied with scales of statute miles. Most of the land measure- 

 ments, and some of those of the sea, were made on Bartholomew's Beduced Ordnance 

 Survey Maps, on the scale of 2 miles to 1 inch. The watersheds were first marked on 

 the map in red ink, and then traced on transparent paper divided into squares of T V^ n 

 of an inch in the side. The number of squares occupied by each drainage area was 

 counted, and, divided by 25, gave the superficies in square miles. 



Classed according to their drainage areas the natural divisions of the Clyde Sea Area 

 fall into four distinct groups. Loch Eck, and consequently also the Holy Loch, have by 

 far the greatest catchment area compared with water surface, and although much less 

 extreme, Loch Goil and Loch Lomond may also be classed as having a drainage area 

 more than ten times as extensive as the water surface. Loch Long, Loch Kidun and 

 the Kylcs, and Loch Fyne come together with a land drainage about seven times as large 



