264 BATHYMETKICAL SURVEY OF 



is about 270 square miles, or ten times the area of the loch. The maximum 

 depth recorded by the Lake Survey was 623 feet, while on the Admiralty 

 chart of Lach Lomond a maximum of 105 fathoms, equal to 630 feet, is 

 shown, but there is no indication of the level of the water at the time of 

 the Admiralty survey. The volume of water contained in the loch is 

 estimated at 92,805 millions of cubic feet, or over one half of a cubic 

 mile ; in this respect Loch Lomond ranks second among the Scottish 

 lakes, being exceeded only by Loch Ness, the capacity of which is about 

 three times greater. The mean depth of the entire loch is estimated at 

 only 121 feet, less than 20 per cent, of the maximum depth, which indicates 

 that a large proportion of the lake-floor is covered by shallow water. As 

 a matter of fact, more than two-thirds of the lake-floor is covered by 

 less than 100 feet of water, as shown in the following table, giving the 

 approximate areas between the consecutive contour-lines drawn in at equal 

 intervals of 100 feet, and the percentages to the total area : 



Feet. Acres. Per cent. 



to 100 11,881 ... 67-6 



100 200 2,880 ... 16-4 



200 300 974 ... 5-5 



300 400 528 ... 3-0 



400 500 450 ... 2-6 



500 600 767 ... 4-4 



Over 600 85 ... 0-5 



17,565 100-0 



This table shows a gradually decreasing area with increasing depth 

 down to the 500-feet contour, but then a striking increase in the area is 

 indicated for the zone between 500 and 600 feet, compared with the two 

 shallower zones, denoting that the deepest part of the loch partakes of 

 a flat-bottomed character. 



The bathymetrical conditions in Loch Lomond having been so long 

 known, may be here referred to briefly. The conformation of the entire 

 loch is complex, but especially so in the wide southern portion, where the 

 contour lines of depth are sinuous in the extreme, but even the narrow 

 northern portion, which might be looked upon as a characteristic elongated 

 Highland loch, is to a certain extent irregular. There are three distinct 

 50-feet basins, separated by shallow water (1) at the entrance of the 

 Douglas water, and (2) at the chain of islands consisting of Inchtavanach, 

 Inchconnachan, Inchmoir, Inchcruim, Inchfad, and Inchcailloch, to the 

 south of which chain the water is all less than 100 feet in depth. There 

 are two 100-feet basins, one lying between the chain of islands mentioned 

 and the entrance of the Douglas water, the other extending northwards 

 uninterruptedly from the Douglas water delta to near the head of the loch. 

 There are three 200-feet basins : a small one about a mile from the head 

 of the loch having a maximum depth of 206 feet, a larger one south of 

 the entrance of the Douglas water, circling round Koss point, having a 



