THE FRESH-WATER LOCHS OF SCOTLAND. 



2 < 



FIG. 3. CROSS-SECTIOW OF 



LOCH KATRINE. THE 



BLACK PORTION SHOWS 

 THE TRUE SLOPES; THE 

 OUTLINE SHOWS THE 

 SLOPES EXAGGERATED 



TEN TIMES. 



The bulk of water con- 

 tained in the loch is esti- 

 mated at 27,274,000,000 

 cubic feet, or about one- 

 fifth of a cubic mile, and 

 the mean depth (suppos- 

 ing the loch to be of 

 uniform depth over its 

 present area) at 199 feet 

 (33 fathoms), the mean 

 depth being over 40 per 

 cent, of the maximum depth. The length of the 

 loch is 85 times the maximum depth, and 211 

 times the mean depth. 



The surface of the loch is, according to the 

 Ordnance Survey maps, at an elevation of 364 

 feet above sea-level, so that our survey shows 

 that a considerable portion of the bottom of 

 the loch (equal to about 645 acres, or over one 

 square mile) lies below sea-level, the deepest part 

 being 131 feet (or 22 fathoms) below the level 

 of the sea. The area below the level of the 

 sea is indicated by a red line on Plate IV. In 

 this respect Loch Katrine differs from the other 

 lochs referred to in this paper, for in none of them 

 is the depth sufficiently great to bring any portion 

 of their bottoms below the level of the sea. 



The soundings show that Loch Katrine prac- 

 tically forms a single basin, not being divided, like 

 Loch Lomond and Loch Lubnaig, for instance, 

 into separate basins by any important ridges or 

 rises on the bottom. The deepest part is in the 

 centre of the loch, a long narrow depression, with 

 depths exceeding 400 feet, extending for over 4 

 miles from opposite Coilachra to opposite Ruinn 

 Dubh-aird, with a maximum width of over a quar- 

 ter of a mile ; this 400-f eet depression has an area 

 of about 515 acres, or 17 per cent, of the entire 

 superficial area of the loch. The deepest sounding 

 (495 feet) is situated at the very eastern extremity 

 of the 400-f eet depression. 



The 300-feet depression is over 5 miles in 

 length, with a maximum breadth of one-third of a 

 mile ; it extends from off Coilachra to near Ellen's 

 isle. The area enclosed between the 300-feet and 



