220 BATHYMETRICAL SURVEY OF 



Loch Meallan an Fhudair to Loch Maree, and has tapped Lochan Fada, 

 slightly lowering its level, thus beheading Abhuinn Gleann na Muic. 



The height of the loch above sea-level was not determined by the 

 Ordnance Survey, nor by the Lake Survey when sounded on July 25 

 to 28, 1902, owing to absence of bench-marks, but, judging from the 

 spot-levels and the 1000-feet contour-line, its level must be about 1005 

 or 1006 feet above the sea. 



The length of Lochan Fada is 3| miles, and its maximum breadth 

 nearly two-thirds of a mile; the mean breadth is over one-third of a 

 mile. Its waters cover an area of nearly 1J square miles, and it drains 

 an area 6J times greater, or over 9J square miles. The maximum 

 depth is 248 feet ; this occurs in the centre of the loch off the mouth of 

 Allt Meallan a' Chruidh. The mean depth is estimated at 102 feet, and 

 the volume at 4091 millions of cubic feet. The breadth of the loch at 

 the position of the deepest sounding is twelve times the depth. The 

 shore development is 2-16, and the insulosity is nil ; Lochan Fada, like 

 so many of the larger lochs, has not a single island. 



The bottom of Lochan Fada is very regular, the 50-feet and 100-feet 

 areas being continuous, and extending almost from one end of the loch 

 to the other. The main 150-feet area extends from west of Claona to 

 the narrower part of the loch, and has a length of 1J miles; there is t* 

 small 150-feet area near the south-east end of the loch. The 200-feet 

 area extends from south-west of Claona to west of Allt na Botaig ; its 

 length is one mile, and average width 280 yards. 



The areas between the consecutive contour-lines, and the per- 

 centages to the total area of the loch, are as follows : 



Oto 60 feet 230 acres 25 -0 per cent. 



50,, 100 ,, 236 25-7 



100,, 150 263 28-7 



150,, 200 100 10-8 



Over 200 , 90 , 9 '8 



919 , 100-0 



It is unusual to observe, on proceeding from the shore into deeper 

 water, an increasing area between the contour-lines drawn at regular 

 intervals, as in the case of Lochan Fada, and indicates an average steep 

 slope near shore. A glance at the map shows that the 50-feet contour 

 follows closely the outline of the loch, and in places approaches very 

 close to the shore. 



Seiche. On July 28, beginning at 1 p.m., a well-marked seiche was 

 observed in Lochan Fada in a sheltered bay at the south-west end of 

 the loch ; the wind was strong from the west. The amplitude was half 

 an inch, and the period about 11-6 minutes; but this oscillation was so 

 broken up by two other oscillations, whose periods were about 2J 



