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. 
‘‘ Stokm- Weather ” at Fort Augustus. 
Notes communicated by Uom 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 ” (Le. 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. 
