THE FRESH- WATER LOCHS OF SCOTLAND. 221 



minutes and 1 minute respectively, that the whole effect was extremely 

 complicated, and no calculations could be made from the observations. 

 Temperature Observations. The temperatures taken in Lochan Fada 

 are extremely interesting, because they indicate a much lower tempe- 

 rature than was observed in any of the other lochs in the district at the 

 same time of the year, as shown by the following series taken at 6.40 

 p.m. on July 28, 1902, to the south of Allt Meallan a' Chruidh : 



Surface 51'l Fahr. 



10 feet 51'l 



20 ... 51'l 



50 51-0 



75 45-8 



100 45-0 



150 44-3 



220 44-l 



This series indicates an almost constant temperature down to 50 

 feet, then a fall of 5-2 between 50 and 75 feet (a fall exceeding 1-0 per 

 5 feet of depth), and then a slight decrease of l-7 down to the bottom in 

 220 feet. Compared with the larger and deeper Loch Maree, the water 

 in Lochan Fada was found to be colder at all depths than that in Loch 

 Maree : thus the surface of Lochan Fada had a temperature about 3| 

 lower than was observed in the surface waters of Loch Maree a week 

 earlier, and at the bottom of Lochan Fada, in 220 feet, the temperature 

 was found to be about 1J lower than at the bottom of Loch Maree in 

 350 feet. This is probably due to the fact that Lochan Fada is very 

 deep, considering its area, and therefore a large volume of water has to 

 be warmed, while only a comparatively limited area is exposed to the 

 heating agencies. 



Loch Garbhaig (see Plate XLVL). Loch Garbhaig lies between 

 Lochan Fada and Loch Maree, about half a mile from the former and 

 1^ miles from the latter. It drains into Loch Maree by the Amhainn 

 na Fuirneis, which leaves the loch at its western end, and, flowing in a 

 westerly direction, enters Loch Maree between Furness and Letterewe. 

 The ground at the eastern end is not much elevated above the surface of 

 the loch, the col leading over to Lochan Fada, but on the south side 

 Slioch rises up from the shore to a height of 3200 feet, and on the north 

 side the high ground to the east of Beinn Lair rises to over 2500 feet. 

 The most noticeable feature of the surrounding country is its bareness. 

 The height of the loch above the sea was not determined by levelling 

 when surveyed on July 25, 1902, but from the contour-lines the level 

 is probably between 1005 and 1015 feet. 



Loch Garbhaig is over a mile in length, with a maximum breadth 

 of nearly one-third of a mile, the mean breadth being one-fifth of a 

 mile. Its waters cover an area of about 148 acres, and it drains an 



