THE FRESH- WATER LOCHS OF SCOTLAND. 429 



In the reports of the Balatonsee Commission, mirages of a similar 

 nature are discussed. Von Cholnoky explains how they arise through 

 the formation of a lower stratum of warmer air, heated from the lake. 

 In shallow lakes like Lake Balaton, the mirage is essentially a summer 

 phenomenon. The lake remains warm during the night when the air 

 cools. 



In Loch Ness the converse is the case. The great body of water 

 maintains a moderate temperature throughout the year. In summer 

 the lake rarely attains to 60-0 Fahr., and so the air may frequently 

 remain as warm as the lake, though mirages may occur after any cold 

 night. In winter the lake maintains a high temperature, rarely falling 

 below 42-0 or 43 0< Fahr., and thus the air will fall to a much lower 

 temperature almost every night, and a well-marked layer of warmer 

 air be formed by morning over the surface of the lake, giving rise to the 

 mirage. 



" STORM- WEATHER " AT FORT AUGUSTUS. 

 Notes communicated by Dom CYRIL VON DIECKHOFF. 



The general features of well-developed " storm-weather " are low 

 barometer, dry haze, wind usually south-east, blowing in isolated gusts 

 (''isolated" with regard to space and time), low strata of cloud forming 

 along lines parallel to the Great Glen, small cumuli forming rapidly in 

 the air and drifting towards the north-west, where they mass and form 

 large strata, often of very dark and threatening appearance. Little or 

 no rain falls during the perfect type, but rain often comes when it 

 breaks up. These small cumuli are well known as indications of 

 gales from the south-east, and are called by the local sailors " Pack- 

 merchants " (i.e. pedlars). There are various sub-species of this kind 

 of weather, especially one where the wind is constantly shifting in 

 every direction, the clouds all the while coming from the south-east. 



In another type there is a north-east wind (warmer than the ordinary 

 north-east wind), while the clouds come from the south-east. On these 

 occasions the height of the lowest cloud is never much above 3000 feet. 

 There are often several layers at different heights, all in a north-east 

 to south-west direction even alto-stratus pieces lie occasionally in this 

 direction ; their motion is usually very slow ; cirrus comes slowly from 

 the south-west. 



" Storm- weather " may occur at any time of the year. The strongest 

 gales, or at least the fiercest gusts, which we get on the loch, come from 

 the south-east. On very rare occasions there has been noticed a kind 

 of reverse to the " storm-sky " during a north-west wind. 



