136 BATHYMETRICAL SURVEY OF 



The reservoir did doubtless afford the opportunity, but, as it turned out, it 

 would have been necessary to visit it at very short intervals. In January 

 there was an almost total absence of life ; in the following July the process 

 of stocking was almost completed if all the kinds of life found in old lochs 

 had not arrived, those which had arrived were very well established and 

 distributed all through the water. In January, 1906, a few months after 

 the reservoir was filled, the temperature was 36 Fahr. at the surface. 

 No life whatever was found except a few individuals of a kind of crustacean, 

 a Cyclops not of the common pecies found in lakes. 



"It was not convenient to visit Talla again till July, 1906, when the 

 bathy metrical survey was made. The surface temperature was then 56. 

 The three commonest lacustrine Crustacea were present Daphnia hyalina 

 was scarce; Cyclops strenuus was abundant, but mostly immature, only 

 a few carrying eggs ; Bosmina obtusirostris was in extreme abundance. 

 The plankton rotifers found were Anurcea cochlearis, Polyarthra platyptera, 

 Synchseta pectinata, and Conochilus volvox. Noteus quadricornis, a rotifer we 

 have already found in Scottish lochs, and only in very shallow ones, was 

 fairly abundant at the surface over the deepest part. 



" In March, 1907, the Crustacea were the same, but less abundant, and the 

 two rotifers Notholca longispina and Furcularia reinhardti were observed for 

 the first time. The temperature of the surface was 41, and at 30 feet 39-5. 



" In contrast to the very rapid stocking of Talla is the case of the new 

 reservoir at Holl, in the Lomond Hills, in Fife, where we found none of the 

 common lake organisms after the reservoir had been open for a year or 

 two. In Logan reservoir, after three or four years of existence, the 

 phytoplankton was found very well developed, the diatoms imparting a 

 yellowish colour to the water, but the zooplankton was much less abundant. 

 These contrasted instances show how little we yet know about the factors 

 governing the stocking of a new lake." 



Loch of the Lowes (see Plate XLIX.). The Loch of the Lowes 

 lies at the head of St. Mary's Loch, into which it flows by a stream 

 about 150 yards in length, the fall between the two lochs being only about 

 a foot; at one time they probably formed a continuous sheet of water. 

 The loch is rectangular in outline, and trends almost north and south, 

 being nearly a mile in length, and less than a quarter of a mile in 

 maximum breadth. The superficial area is about 99 acres, and the 

 drainage area exceeds 10 square miles. The maximum depth of 58 feet 

 was observed towards the southern end of the loch. The volume of 

 water is estimated at 1 57 million cubic feet, and the mean depth at 36J 

 feet, or nearly two-thirds of the maximum. The basin is simple in con- 

 formation, and flat-bottomed in character, as is shown by the fact that, 

 while 25 per cent, of the lake-floor is covered by less than 25 feet of water, 

 34 per cent, is covered by more than 50 feet of water, although the 

 maximum depth is only 58 feet. The loch was surveyed on May 5, 1905, 



