272 
BATHYMETRICAL SURVEY OF 
but since it receives the outflow from all the lochs described in the 
preceding pages, its total drainage area is very large — about 149J 
square miles, an area 85 times greater than the area of the loch. The 
maximum depth of 164 feet was observed about miles, or about 
one-third of the length of the loch, from the north-west end. The 
volume of water is estimated at 3288 millions of cuHic feet, and the 
mean depth at nearly 67 feet. The loch was surveyed on August 16, 
1902, when the elevation of the lake-surface was found to be 249*8 feet 
above the sea. 
The floor of Loch Luichart is irregular, there being three 50-feet 
basins separated by shallower water. The largest and deepest lies in the 
wider north-western half of the loch, and is about 2J miles in length, 
approaching to within less than 200 yards from that end. The central 
50-feet basin is separated from the north-western basin by an interval of 
half a mile, in which lies the single small island in the loch, and where 
the depth in the centre at another place is only 5 feet, and is over IJ 
miles in length. Immediately to the south-east of this central basin 
there is a narrow constriction in the outline of the loch, in which a 
depth of 16 feet was recorded, succeeded by a slight expansion contain- 
ing the third 50 -feet basin, with a maximum depth of 55 feet and of 
small extent. The principal 100-feet basin in the north-western part 
of the loch is nearly 2 miles in length, and encloses the deepest part of 
the loch. Two small subsidiary 100-feet basins lie within the central 
50-feet basin : one based upon an isolated sounding of 100 feet, the 
other near the south-eastern end having a maximum depth of 115 feet. 
The 150-feet basin is nearly a mile in length, and is distant three- 
quarters of a mile from the north-west end of the loch ; the maximum 
depth of 164 feet was recorded near the south-eastern end of the basin. 
It is curious to note the difference in the outline of this 150-feet basin 
as compared with the outlines of the 50 and 100-feet basins enclosing 
it, for, while the shallower contours follow approximately the shore- 
line, and therefore enclose areas widest towards the north-west and 
narrowing gradually in the opposite direction, the 150-feet basin is 
widest towards the south-east and narrows gradually to the north-west 
as the outline of the loch widens out. At the same time the deep basin 
approaches nearer to the northern shore at its north-west end, while it 
approaches nearer to the southern shore at the opposite deeper end, so 
that at the position of the deepest sounding the slope off the southern 
shore is much steeper than off the northern shore, as is well brought out 
in the cross-section C-D on the map. The longitudinal section A-B 
down the centre of the loch shows the three basins included in the loch, 
each successively deeper on proceeding towards the north-west end. 
The areas between the consecutive contour-lines, and the percentages 
to the total area of the loch, are as follows: — 
