THE FRESH-WATER LOCHS OF SCOTLAND. 
203 
practically uniform from the surface to the bottom at a depth of 1010 
feet, the surface temperature being 41°*9, while that at the bottom was 
41°-8, a range of only 0°-l, and on October 23 of the same year the varia- 
tion was from 50°'2 at the surface to 43°‘0 at the bottom in 1000 feet, a 
range of 7°-2. The temperature at the depth of 1000 feet has generally 
been regarded as fairly constant at about 42°-0 all the year round, with 
a variation of about 0°-2, and this higher record of 43°-0 may be due to 
the increased amount of water draining into the loch during the wet 
summer of 1903. The highest surface temperature recorded was one 
FIG. 36. FALLS OF MORAE. 
(Photograph by Mr. T. N. Johnston, M.B., C.M., F.R.S.E.) 
of 59°*2 on June 30, 1902, off Bracora, the air temperature at the time 
being 62°-8, with a moderate westerly breeze. This gives a total range 
of 17°'4 between the highest surface and the lowest bottom temperature 
recorded. 
Deposits . — The deposits covering the floor of Loch Morar are mostly 
dark brown in colour, which becomes almost black in the deeper parts. 
A sample from 1000 feet was dark brown when wet, and greyish-black 
when dry, containing about 50 per cent, of black vegetable matter, 
about 10 per cent, of mineral particles (quartz, mica, hornblende, &c.), 
with a mean diameter of 0*15 millimetre, and about 40 per cent, of 
amorphous clayey matter, with many fine Diatoms and a few fragments 
