102 BATHYMETR1CAL SURVEY OF 



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 ^0 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 60'OFahr. 



10 feet 59-5 ,, 



13 57'0 



15 52-2 



20 51-0 



30 50-2 ,, 



40 50-0 



50 ,, 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 0> 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, 



