170 IV. CLIMATE. 



south-east of England ; thus being in excess over the 

 average difference for places little above the sea level in 

 Mid Britain. Some circumstances suggest that the sum- 

 mer temperature of the Highland mountains is higher 

 than might be expected, if compared with that of low 

 places in their vicinity ; but no proper means or averages 

 can here be stated. A remarkable fact, some time ago 

 noted by the writer of this work, seems worthy of record 

 by way of illustration, even though a solitary one. Very 

 near the summit of Ben Aulder, near Loch Erricht, in 

 Westerness, is a shallow pool of water, on a bed of dark 

 rock, say (from recollection) a quarter to half an acre in 

 extent, and at an altitude of about 3500 feet. On July 

 24, 1841, the temperature of this pool was tried by a 

 Fahrenheit thermometer, in the middle of a clear and 

 calm day, and found to be 59. At this time, the cold 

 water from a large patch of snow, melting under the 

 bright sun, was trickling into the pool at one end. The 

 temperature of the long and deep Loch Erricht, at an 

 altitude of 1200 feet, a few hours later on the same day, 

 was found to be only 48. The high temperature of small 

 sphagnous swamps is often quite sensible to the hand, on 

 sunny days, at a considerable elevation. These and 

 other analogous facts show that the heating power of the 

 sun's rays is very great on the higher mountains during 

 serene days. But so many days there are neither calm 

 nor clear, that such a temperature as 59, above recorded 

 for the pool on Ben Aulder, may be only a rare and 

 exceptional instance. 



15. Extremes of Temperature, — Every observer of such 

 matters is familiar with the fact, that most of the plants 

 kept in greenhouses during winter, and removed to the 

 open ground of the gardens during summer, are sue- 



