20 
BATHYMETRICAL SURVEY OF 
LOCHS OF THE FORSS BASIN. 
The Lake Survey staff sounded the two principal lochs within this basin, 
viz. Lochs Calder and Shurrery. The few smaller lochs — of which the 
most important are Loch Olginey flowing into Loch Calder, and Loch 
Chaluim flowing into Loch Shurrery — could not he surveyed for lack of 
boats. The headwaters of the basin take their rise on the flanks of Beinn 
nam Bad Mhor and Cnoc an Fhuarain Bhain, flowing by the Cnocglass 
or Torran water into Loch Shurrery, from which issues the Forss water, 
which on its way to the sea is joined by the Alltan Ghuinne, bearing the 
overflow from Loch Calder. Like most of the Caithness lochs. Loch 
Shurrery is shallow, while Loch Calder is important both on account of 
its depth, and because it is the source of the water-supply to the town of 
Thurso. The fishing in both lochs is good, though preserved ; salmon and 
trout being got in Loch Shurrery, and trout and char in Loch Calder. 
Loch Shurrery (see Plate VII.). — Loch Shurrery lies about 8 miles 
from Thurso and 7 miles from Reay, on the north coast of Caithness. 
The loch trends in a north and south direction, and is miles in length, 
the maximum width being less than half a mile. Its waters cover an area 
of about 228 acres, or over one-third of a square mile, and it drains an 
area of 29 square miles. The maximum depth of 7 feet was observed in 
two places — near the middle of the loch towards the eastern shore, and 
near the foot of the loch towards the western shore. The volume of water 
is estimated at 43 million cubic feet, and the mean depth at 4| feet. The 
loch was surveyed on October 6, 1902, when the elevation of the lake- 
surface was found to be 321*45 feet above the sea ; when levelled by the 
Ordnance Survey officers on June 4, 1870, the elevation was 321*1 feet 
above sea-level. Loch Shurrery is a shallow, flat-bottomed basin, the 
majority of the soundings having been taken in depths of 5 and 6 feet, 
while three soundings were taken at the maximum depth of 7 feet — two 
near the centre and one near the northern end, as already indicated. The 
area of the lake-floor covered by more than 5 feet of water is about 121 
acres, or 53 per cent, of the total area of the loch. The temperature of 
the surface water towards the southern end was 50°*0 Fahr., while towards 
the northern end readings at the surface and at a depth of 3 feet gave 
49°' 5, and a reading at 5 feet gave 49°*2. 
