THE FKESH- WATER LOCHS OF SCOTLAND. 243 



which is nearly flat-bottomed, but slightly deeper towards the east side, the 

 greatest depth is 12 feet. In the southern basin the maximum depth of 13 

 feet is close to Quoy ness, and it gradually shoals to the south end of the 

 loch. This basin is constricted in the middle by the Castle Holm and a 

 number of other islands. In superficial area, which is 331 acres, or about 

 half a square mile, the Loch of Strom is the largest, as it is also the 

 longest, in Shetland. The low mean depth, 7 feet, gives a relatively small 

 volume of only 101 millions of cubic feet, which is equalled by one loch 

 (Clings Water), and exceeded by four lochs (Eela, Cliff, Spiggie, and 

 Girlsta). 



The Loch of Strom has an extensive drainage area, including Sand 

 Water, and the whole central valley of the Mainland for almost 6 miles 

 north, or almost as far as Voe. The upper part of this valley, where 

 the stream flows south from Petta Water, is known as Tetta vale; after 

 passing through Sand Water it becomes Sandwater burn, and flows into 

 the north end of the Loch of Strom, under the name of Strom Firth burn. 

 The drainage area extends to nearly 8 square miles, or about half a square 

 mile less than that of the Loch of Cliff. The surface temperature varied 

 from 56-8 to 57-2 Fahr. in different parts of the loch. 



Loch of Tingwall (see Plate CIII.) is a fairly large loch of oblong 

 form, 4 miles west of Lerwick, and 2 miles north of Scalloway. It 

 occupies, with the Loch of Asta, a narrow valley running across the 

 Mainland, nearly from north to south, between Tax firth and Cliff sound. 

 The whole west side of the loch is cultivated, with high hills rising 

 behind; on the east is moorland, with sparse heather. At the north 

 end is a flat strip of meadow, liable to floods. On the western shore 

 are a few large boulders and bosses of rock. The island in the centre is 

 low and covered with heather. The length is just over a mile, and the 

 greatest breadth nearly a quarter of a mile. 



The loch is divided into two nearly equal portions by a constriction, 

 where it is also very shallow, the depth in the centre of the narrows being 

 only 9 feet. It is still shallower in the channels on either side of the 

 island north of the narrows, where the depths are only 2 and 3 feet. The 

 northern basin is the shallower. It is almost flat-bottomed over the 

 greater part of the area, with depths of from 7 to 9 feet. In the centre is 

 a very small and abrupt depression, in which there is a depth of 40 feet. 

 The southern basin is of a different character ; as shown by the contours, 

 the sides slope fairly regularly to the centre, where there is the maximum 

 depth of 60 feet. The mean depth is about 19 feet, the area nearly 107 

 acres, and the volume of water 87 millions of cubic feet. No large streams 

 enter the loch ; its outflow is to the south, by a stream about 100 yards 

 long, into the Loch of Asta. There is rock close to the outflow, on the 

 west side, and the burn flows among stones, with rock in the channel a 

 few yards from the loch. 



