THE FRESH-WATER EOCHS OF SCOTLAND. 
15 
where the deposit is white and calcareous, and it was a regular practice 
some few years ago to dredge the loch to the south of the island, and 
to use the mud for marling the land. 
Loch Watten (see Plate III.). — Loch Watten, the largest of the Caith- 
ness lochs, is situated about midway between Wick and Thurso, the 
railway between those places running along its northern shore, and the 
main road skirting its southern shore. The loch trends in a north-west 
and south-east direction, with a slight sinuosity in the outline, the upper 
portion being narrower than the main body of the loch, and bending in a 
northerly direction. It is 3 miles in length, with a maximum breadth 
towards the lower end of three-quarters of a mile, the mean breadth being 
about half a mile. Its waters cover an area of about 930 acres, or about 
1| square miles, and it drains directly an area of over 13 square miles, but 
since it receives the overflow from Loch Scarmclate its total drainage area 
is about 20| square miles. The maximum depth observed w^as 12 feet, 
and no fewer than thirty-six soundings were taken at this depth in the 
south-eastern half of the loch. The volume of water is estimated at*»341 
million cubic feet, and the mean depth at 8| feet. The loch was surveyed 
on October 8 and 9, 1902, when the elevation of the lake-surface was 
found to be 54'9 feet above the sea; when levelled by the officers of the 
Ordnance Survey on December 28, 1869, the elevation was 55*4 feet above 
sea-level. According to the miller at Watten, the wind sometimes per- 
ceptibly affected the level of the water, and after an easterly wind had 
been blowing strongly for some time it was impossible for him to work 
the mill, the water being driven before the wind and piled up at the 
north-west end. The water might rise 2 feet above, and fall 1 foot 
below, the level on the date of the survey. 
Loch Watten may be described as a large, shallow, flat-bottomed 
basin, the deeper portion lying towards the south-eastern end, the water 
shoaling more gradually on proceeding towards the north-western end. 
The great majority of the soundings were taken in depths exceeding 
5 feet, and more than one half of the lake-floor is covered by more than 
10 feet of water. The mean depth of the entire basin is 70 per cent, of 
the maximum depth. The temperature of the surface water at 10 a.m. on 
October 8, 1902, was 49°*9 Fahr., and at 10 a.m. on October 9, the surface 
temperature was 49°*6, while a reading at 12 feet gave 49°*5. 
Loch Hempriggs (see Plate III.). — Loch Hempriggs lies about 2 miles 
to the south-west of the town of Wick, and within a mile of the shores of 
the North Sea, though the outflowing stream pursues a long and devious 
course in a northerly direction before joining the Wick water on its way 
to the sea. The loch is irregularly subcircular in outline, and the 
maximum diameter from north to south and from east to west is in 
each case about three-quarters of a mile. The superficial area is about 
