THE FRESH- WATER LOCHS OF SCOTLAND. 165 



two miles in length ; it encloses two small 100-feet basins with maximum 

 depths of 113 and 103 feet respectively, separated by a rise of the bottom 

 on which the depth is 82 feet. The areas between the consecutive 

 contour-lines, and the percentages to the total area of the loch, are 

 as follows : 



Oto 25 feet 230 acres 38 '8 per cent. 



25 50 ,, 215 36-2 



50,, 75 94 15-9 



75 100 38 6-4 



Over 100 , 16 . 2'7 



593 . 100-0 



Thus 75 per cent, of the lake-floor is covered by less than 50 feet of 

 water. Loch Veyatie was surveyed on August 29 and September 8, 

 1902. On commencing the survey 011 August 29, the elevation of the 

 lake-surface was determined, by levelling from bench-mark, as being 

 364-8 feet above the sea ; in the interval between the two days devoted 

 to the survey the water rose to the extent of 15 inches, then gradually 

 fell again, and on September 8 the elevation was found to be 365-6 feet 

 above the sea. The soundings taken on the last-mentioned date have 

 been corrected accordingly, in order to bring them into agreement with 

 those taken on the earlier date. The boatman stated that the water in 

 the loch was about its lowest level on August 29, 1902, and the highest 

 drift-mark seen was 3 feet above the surface of the water on that date. 

 The officers of the Ordnance Survey found the level of Loch Veyatie 

 to be 365-7 feet above the sea on September 8, 1870. Temperature 

 observations taken at 3.30 p.m. on September 8, 1902, indicated an 

 almost uniform temperature throughout the waters of the loch, the 

 readings at the surface and at a depth of 50 feet being identical (55'9), 

 and at a depth of 100 feet 55-8. 



Loch a' Mhiotailt (see Plate XXXVIII.). Loch a' Mhiotailt 

 (pronounced Vattle) lies immediately to the south-west of Loch Veyatie ; 

 in fact, they may almost be looked upon as one loch, for after heavy 

 rains there is a channel about 20 feet in length, 10 feet in breadth, and 

 1 foot in depth connecting the lochs. When the water is low, however, 

 the separation is complete, the barrier being formed by one of the basic 

 dykes so numerous in this part of the gneiss : the rock is in places 

 covered by a thin layer of sand. The ground around the loch rises 

 steeply up to a height of 100 to 200 feet above the surface of the water, 

 so that the loch is almost shut in, and only towards Loch Veyatie can 

 any opening in the wall of rock be seen. Loch a' Mhiotailt is over 

 half a mile in length from east to west, the maximum breadth exceeding 

 a quarter of a mile, the mean breadth being about one-seventh of a mile, 



