THE FRESH- WATER LOCHS OP SCOTLAND. 157 



largest volume of \vater of the Spey lochs, it is inferior in superficial area 

 to Loch Morlich. Of irregular outline, it exceeds a mile in length from 

 south-west to north-east, from inflow to outflow, and from east to west 

 the diameter is little less than a mile, the mean breadth being nearly half 

 a mile. The superficial area is about 280 acres, or less than half a square 

 mile, and the total drainage area exceeds 316 square miles, including the 

 other lochs lying above it. The maximum depth of 100 feet was observed 

 towards the south-eastern shore. The volume of water is estimated at 454 

 million cubic feet, and the mean depth at over 37 feet. When the loch 

 was surveyed on October 9, 1903, the elevation could not be determined, 

 but was estimated to be about 4 feet higher than shown on the Ordnance 

 Survey map, where the elevation is given as 721 '4 feet above the sea, 

 though the date when levelled is not indicated, the water being rather high, 

 and flooding the shore in some places. Weeds were abundant at the inlet 

 and outflow of the river. The floor of the loch is somewhat irregular, as 

 shown by the sinuosity of the contour-lines, apparently brought about by 

 the deposition of material by the inflowing river, the contour-lines being 

 pushed out into the centre of the loch. The deep water lies in the 

 eastern portion of the loch, sending out a tongue along the western shore 

 into the south-western portion of the loch. Nearly one-half of the lake- 

 floor is covered by less than 25 feet of water. The temperature of the 

 water was practically uniform from surface to bottom, the readings at the 

 surface and at 50 feet being identical, viz. 45-3 Fahr., while a reading at 

 85 feet gave 45-l. 



Loch Alvie (see Plate LIX.) is situated about 2 miles south-west of 

 Aviemore, and about 8 miles north-east from Kingussie. It is irregular in 

 outline, consisting of a wide central portion, sending out an arm to the 

 west and another arm to the north-east. The loch is nearly a mile in 

 length, with a maximum breadth of almost half a mile, covering an area of 

 about 139 acres, and draining an area of 11 square miles. The deepest 

 part lies in the north-eastern portion of the loch, the maximum depth of 

 70 feet having been observed less than one-third of a mile from the north- 

 east end. An isolated deep basin was also found in the western part of 

 the loch, soundings in 50 and 52 feet being recorded less than one-third 

 of a mile from the west end, while the wide central portion is less than 50 

 feet in depth. One-half of the lake-floor is covered by less than 25 feet of 

 water. The volume of water is estimated at 163 million cubic feet, and 

 the mean depth at 27 feet. The loch was surveyed on October 9, 1903, 

 but the elevation could not be determined ; from spot-levels the elevation 

 is apparently about 685 feet above the sea. The surface temperature was 

 47-0 Fahr. 



Loch Gamhna (see Plate LX.), the smallest of the Spey lochs surveyed, 

 lies about 2 miles to the south-east of Loch Alvie, on the opposite bank of 



