102 
BATHYMETRICAL SURVEY OE 
the maximum depth, and 360 times the mean depth. The Loch of 
Lowes forms on the whole a simple basin, but with here and there 
minor undulations of the bottom. The maximum depth of 53 feet was 
observed approximately in the centre of the loch, but a short distance 
to the north of it a sounding of 42 feet was taken apparently surrounded 
on all sides by shallower water, and to the west a depth of 7 feet was 
observed with deeper water all round. Generally speaking, the slope 
of the bottom is gentle, there being no evidence of any steep gradients. 
The area of the lake-floor covered by less than 20 feet of water is about 
120 acres, or 55 per cent, of the total area of the loch; that covered by 
water between 20 and 40 feet in depth is about 79 acres, or 26 per cent. ; 
and that covered by more than 40 feet of water is about 19 acres, or 
9 per cent, of the entire area of the loch. The Loch of Lowes was 
surveyed on June 2, 1903, the same day as the Loch of Craiglush, and 
the elevation of the two lochs above the sea was found by levelling to be 
identical, viz., 327'6 feet. When levelled by the Ordnance Survey 
officers on July 13, 1899, the elevation was found to be 327*9 feet above 
the sea. 
Temperature Observations . — Temperature observations taken in the 
deepest part of the loch at 1.15 p.m. gave the following results: — 
Surface 
10 feet 
13 „ 
15 „ 
20 „ 
30 „ 
40 „ 
50 ,, 
60° *0 Eahr. 
59° -5 „ 
57° -0 „ ^ 
52°-2 „ 
51° -0 „ 
50° -2 ,, 
50° -0 „ 
50° -0 ,, 
This series shows a range of 10° in the temperature throughout the 
50 feet of water,; the greatest fall being one of 4°*8 between 13 and 15 
feet. Compared with the temperatures taken in the Loch of Craiglush 
earlier in the day, this series shows a smaller range (the temperature at 
the surface being lower and at the bottom higher, notwithstanding the 
greater depth), and the position of the greatest fall in the temperature 
was observed at a greater depth, viz., between 10 and 15 feet, as 
compared with between 8 and 10 feet in the Loch of Craiglush. 
Loch of Butter stone (see Plate XXIX.). — The Loch of Butterstone 
(or Butterston) is, like the two neighbouring lochs, to a large extent 
surrounded by trees; its shores are sandy or weedy, and many coots 
nest among the weeds. It is almost circular in outline, the greatest 
diameter (or length) from north-east to south-west being about three- 
fifths of a mile, while the maximum breadth from north-west to south- 
east is about half a mile, the mean breadth being over a quarter of a mile, 
or 50 per cent, of the length. Its waters cover an area of about 108 acres. 
