502 THE FRESH-WATER LOCHS OF SCOTLAND 
the dam consisting of the Lintrathen porphyry. Tlie locii is much 
silted up by the Melga Water^ which flows through it. 
LiTTLESTER. — In drift on gneiss. 
Loch. — Rock-basin in schists and Hmestones between the quartzites of 
Ben-y-Ghloe. 
LocHABER. — Lies partly on granite^ partly on Silurian greywackes, and 
partly on glacial deposits. 
LocHENBRECK. — In drift resting on Silurian greywackes and shales. 
LocHiNDORB. — Hollow in fluvio-glacial deposits. 
LocHiNVAR. — Lying partly on Silurian greywackes and shales and partly 
in drift. 
LocHNAW, — Small lochan^ partly in greywackes and partly drift-dammed. 
LocHRUTTON. — Partly in Silurian greywackes and shales and partly in drift. 
LocHY. — Rock-basin along shatter-belt of Great Glen fault. 
Lomond. — This lake may be regarded as a typical valley rock-basin lying 
across the strike of the strata in a valley in great part excavated by 
one of the original consequent streams of Scotland draining towards 
the south-east. 
The loch may be divided into two sections: — (1) an upper or 
Highland section, extending from its head to Luss and the islands 
of Inchlonaig and Inchtavannoch lying in metamorphic rocks ; 
(2) a lower or Lowland section, extending from the above-mentioned 
islands to the foot of the loch, partly in Highland schists but chiefly 
in strata of Old Red Sandstone age. 
The upper section is situated in a narrow valley whose direction 
is in great part determined by a system of joints and faults with 
a nearly north-and-south trend. Before the glacial period the con- 
sequent river had excavated a channel across the belt of schistose grit 
which now forms the barrier between the upper and lower sections. 
Throughout the Ice Age the direction of the ice-flow in the present 
region was southerly — that is, approximately, down the loch. The 
basin lies in comparatively soft mica-schists where the valley is 
narrowest and steepest. It is bounded by the 400-ft. contour line, 
and contains two minor basins below the 500-ft. line, within one 
of which occurs the deepest sounding (623 feet). Near Rowardennan 
the outcrop of the Ben Ledi grits crosses the lake, and the upper 
or deep basin suddenly gives place to a shallow plateau with two 
islands, the deepest sounding here being only 49 feet. It is doubt- 
less true that the Douglas Burn has laid down a delta extending 
into the lake from the west shore, and that a spit has been formed 
at Rowardennan on the eastern bank ; but the shallow plateau is 
not due to these accumulations. It may rather be said that its 
existence led to the deposition of these materials. 
Below this barrier a second but shallower basin occurs in the 
upper section. Here the valley widens, and the hills, though high, 
recede to some extent. The lake, however, does not appreciably 
