124 
BATHYMETRICAL SURVEY OF 
the centre of the loch, where depths of 54 to 57 feet were found, with 
depths exceeding 60 feet to the north and south. The northern portion 
of the loch, beyond the narrows at Balnakeilly, is comparatively 
shallow. The area of the lake-floor covered by less than 25 feet of 
water is about 260 acres, or 66 per cent, of the total area of the loch; 
that covered by water between 25 and 50 feet in depth is nearly 100 
acres, or 24 per cent. ; and that covered by more than 50 feet of water 
is over 40 acres, or 10 per cent, of the entire area of the loch. It was 
surveyed on June 25, 1903, and the height of the surface of the water 
above the sea was determined, by levelling from bench-marks, as being 
674'6 feet. 
T einperature Ohservatio7is . — Temperature observations taken in the 
deepest part of the loch gave the following results : — 
Surface 
10 feet 
25 „ 
50 ,, 
55 ,, 
60 „ 
65 ,, 
55° 5 Fahr, 
55° ’2 , , 
54° '0 „ 
52° -5 „ 
50° -8 
48° -2 ,, 
48° -0 „ 
This series shows a i 
ange of temperature from surface to bottom of 
7°*5, the greatest fall being one of 2°*6 between 55 and 60 feet. 
Loch of Forfar (see Plate XXXIII.). — The Loch of Porfar lies 
immediately to the west of the town of Forfar, surrounded by cul- 
tivated fields. It flows by the Dean water into the river Isla, the 
outflow being a broad ditch with no perceptible current on the date of 
the survey, the water in the loch being very low. It contains pike, 
perch, and trout. It trends almost east and west, and is over a mile in 
length, with a maximum breadth of nearly a quarter of a mile, the 
mean breadth being about one-seventh of a mile, or 14 per cent, of the 
length. Its waters cover an area of about 103 acres, or one-sixth of a 
square mile, and it drains an area 14 times greater — an area of over 
2 square miles. Over 60 soundings were taken, the maximum depth 
observed being 29 feet. The volume of water is estimated at 51,232,000 
cubic feet, and the mean depth at 11 J feet, or 39 per cent, of the 
maximum depth. The length of the loch is 195 times the maximum 
depth and 494 times the mean depth. The Loch of Forfar is peculiar 
in conformation, due to the peninsula of Queen Margaret’s inch jutting 
out into the loch about midway along the northern shore. From the 
extremity of Queen Margaret’s inch a submerged causeway runs out, 
on which depths of 1, 2, and 3 feet were found. The deepest water in 
the loch lies to the north and west of the inch and causeway, approach- 
ing quite close to the end of the causeway, where a depth of 28 feet 
was recorded, the maximum depth of 29 feet being found a few hundred 
