362 BATHYMETRICAL SURVEY OF 



the river Pattack, some 9 miles long, into the upper end of Loch Laggan. 

 It is a loch of somewhat irregular form, about a mile long by half a mile 

 broad, its long axis running nearly north-east and south-west. The 

 maximum depth is 58 feet, and the mean depth 14 feet. The volume of 

 water is estimated at 106 million cubic feet. The superficial area is 

 about 173 acres, or fully a quarter of a square mile, and it drains an 

 area of 18 square miles. It receives the greater part of the drainage of 

 the east side of the mountain mass, of which Ben Alder (3757 feet) is 

 the highest peak. In this drainage area are three smaller lochs, which 

 were not surveyed. When surveyed in May, 1904, the height above 

 sea-level was estimated (from spot-levels) at 1419 feet. 



The basin is quite simple, the contours roughly following the 

 irregular outline of the shore, and the deepest part almost in the centre 

 of the loch. The slopes are gentle, except opposite the mouths of the 

 two rivers, both of which have laid down alluvial promontories, with 

 small islands, from which the incline to the deepest water is rapid. The 

 loch is on the whole shallow, for 78 per cent, of the lake-floor is covered 

 by less than 20 feet of water, and 60 per cent, by less than 10 feet of 

 water. 



Temperature Observations. A series of temperatures, taken in the 

 deepest part of the loch, gave 42-6 Fahr. at the surface, 41-4 at 25 

 feet, and 40'8 at 50 feet. 



Lochan na h-Earba (see Plate LXXXV.). The two lochs which 

 bear this name may have formed at no very distant date a single loch, 

 as suggested by the common name and by the appearance of the ground. 

 Be that as it may, they are now two distinct lochs, differing by nearly 

 10 feet in level. In April, 1873, the Ordnance Survey officers found the 

 elevation of the west loch to be 115T7 feet, and that of the east loch 

 1142-3 feet, above sea-level. They lie in a valley which runs nearly 

 parallel to that occupied by Loch Laggan, to the south side of that loch, 

 and distant from it about a mile. Hills of over 3000 feet rise close on 

 the east ; on the west they are separated from Loch Laggan by a ridge 

 of between 2000 and 2500 feet in height. The shores are for the most 

 part wooded. 



The West Loch. This is the larger, broader, and deeper of the two. 

 It lies at an elevation of about 1150 feet, some 330 feet higher than 

 Loch Laggan. It is fully If miles in length, rather less than one-third 

 of a mile in greatest breadth, and a quarter of a mile in mean breadth. 

 The greatest depth is 81 feet, the mean depth over 35 \ feet. It has a 

 superficial area of about 263 acres, or less than half a square mile, and 

 drains an area of fully 5 square miles. The volume of water amounts to 

 408 millions of cubic feet. The loch is fed chiefly by two small streams, 

 coming down from Beinn a' Chlachair, which unite just before entering 

 the loch. A stream, half a mile long, winds through a boggy flat, con- 



