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. 



Temperature Observations. Temperature observations taken in the 

 deepest part of the loch gave the following results : 



Surface 55'5 Fahr. 



10 feet 55-2 



25 54-0 



50 52-5 



55 50'8 ,, 



60 48-2 



65 ... 48-0 



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

 7'5, the greatest fall being one of 2-6 between 55 and 60 feet. 



Loch of For far (see Plate XXXIII.). The Loch of Forfar 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 



