114 BATHYMETRICAL SURVEY OF 



depth. The length of the loch is 148 times the maximum depth and 402 

 times the mean depth. Loch Freuchie forms on the whole a simple 

 basin, but with a few minor undulations of the bottom. The 25-feet 

 basin is sinuous in outline, especially towards the south-east end, and is 

 over 1J miles in length, approaching close to the north-west end, but 

 distant less than a quarter of a mile from the south-east end. The 

 50-feet basin, half a mile in length, is contained in the northern half of 

 the loch, and nearer the eastern than the western shore, the maximum 

 depth of 62 feet having been observed in two places, with soundings of 

 60 feet between them. Cones of alluvium have been formed at the 

 mouths of the Turrerich burns at the northern angle of the loch, and at 

 the entrance of the Allt a' Mhuilimi about midway along the western 

 shore. The area of the lake-floor covered by less than 25 feet of water 

 is about 225 acres, or 65 per cent, of the total area of the loch ; that 

 covered by water between 25 and 50 feet in depth is about 95 acres, or 



27 per cent. ; and that covered by more than 50 feet of water is about 



28 acres, or 8 per cent, of the entire area of the loch. Loch Freuchie 

 was surveyed on June 5, 1903, and the height of the surface of the 

 water above the sea was determined, by levelling from bench-mark, as 

 being 867-45 feet ; when levelled by the officers of the Ordnance Survey 

 on August 17, 1899, the elevation was found to be 870-8 feet above 

 sea-level. 



Temperature Observations, Temperature observations taken in the 

 deepest part of the loch at 7 p.m. gave the following results : 



Surface 58'6 Fahr. 



10 feet 58-3 



15 57'6 ,, 



25 , 53'0 



40 50'0 ,, 



60 49-4 



This series shows a range of temperature from surface to bottom of 

 9-2, there being a fall of 4-6 between 15 and 25 feet, and a further 

 fall of 3-0 between 25 and 40 feet. 



Loch Hoil (see Plate XXXI.). Loch Hoil (or Oyl, or Thuill) lies to 

 the south of Aberfeldy, and flows by the Cochill burn into the river 

 Bran. It contains trout, perch, grayling, and gudgeon. It is sur- 

 rounded by low, rounded, hummocky, heather-clad hills. Its shores are 

 stony ; the bay leading to the outflow is very shallow and full of weeds. 

 It is very irregular in outline, and over one-third of a mile in length 

 from north-west to south-east, under one-third of a mile in maximum 

 breadth from north-east to south-west, the mean breadth being one- 

 seventh of a mile, or 43 per cent, of the length. Its waters cover an 

 area of about 35 acres, and it drains an area six times greater an area 



