160 
BATHYMETRICAL SURVEY OF 
Loch Borralan (see Plate XXXVI.). — Loch Borralan (or Borrolan 
or Boarlan) trends north-west and south-east, and the road from Lairg 
to Inchnadamph runs along its north-eastern shore ; Aultnacallagach 
Inn is situated on the road close to the loch near its south-eastern end. 
The ground around the loch is low except to the north, where Cnoc na 
Sroine rises to 1300 feet; to the south-west the ground is thickly 
covered with peat. The abundance of char in the loch is remarkable 
considering its shallowness. Weeds were seen growing on the bottom 
almost everywhere, and over large areas they reach to the surface. It is 
over a mile in length, with a maximum breadth of nearly a quarter of a 
mile (or about 400 yards), the mean breadth being about one-sixth of a 
mile (or over 300 yards). Its waters cover an area of about 118 acres, 
and it drains an area 34 times greater, or square miles. Over 60 
soundings were taken, the maximum depth observed being 21 feet. 
The volume of water is estimated at 49,324,000 cubic feet, and the mean 
depth at feet. The maximum depth of 21 feet was observed towards 
the south-eastern end, opposite the entrance of the Allt nan Cealgach ; 
in the north-western portion of the loch a maximum depth of 16 feet 
was found, the 10-feet contour-line being continuous almost from end to 
end of the loch. Loch Borralan was surveyed on September 1, 1902. 
The elevation of the lake-surface above the sea was determined, by 
levelling from bench-mark, as being 459*7 feet, which is almost identical 
with that observed by the Ordnance Survey officers on August 31, 1871, 
viz., 459*8 feet. According to the boatman, the water in the loch might 
fall about 4 inches lower than on the date of the survey, and in 
exceptional floods might rise 5 feet higher. Temperature observations 
at 3 p.m. gave identical readings of 56°*7 at the surface and at a depth 
of 16 feet. 
Loch Urigill (see Plate XXXVI.). — Loch Urigill (or Urigall) lies 
less than a mile to the south-west of Loch Borralan. The ground 
around the loch is low and covered with peat. Like Loch Borralan, 
it trends in a north-west and south-east direction; in fact, nearly all 
the lochs in this district generally trend north-west and south-east, as 
will be seen from the small index map (Fig. 27). It is nearly two miles 
in length, with a maximum breadth of nearly three-quarters of a mile, 
the mean breadth being nearly half a mile. Its waters cover an area 
of about 500 acres (or over three-quarters of a square mile), and it drains 
an area 14 times greater, or 11 square miles. Nearly 130 soundings 
were taken, the maximum depth observed being 40 feet. The volume of 
water is estimated at 285,088,000 cubic feet, and the mean depth at 
13 feet. Loch Urigill is, on the whole, very shallow, nearly 99 per cent, 
of the lake-floor being covered by less than 25 feet of water, and weeds 
are abundant in some places. The 10-feet area is continuous from close 
to the north-west end to near the south-east end, opposite the entrance 
