6 Proceedings. 



in the night yield by clay, and disappear under the -warming 

 influences of the sun ; and blue skies and fine weather prevail. 

 Calm weather in summer is fine weather. It would be fine 

 weather generally in winter, but for the fog. The rays of the 

 sun are not powerful enough in winter to evaporate the fog, 

 and it remains with us. 



A good many peoj)le have noticed that fogs are most prevalent 

 in calm weather, but do not know why ; generally it is said 

 that if only a wind would spring up, the fog would be blown 

 away. To a certain extent that is right, but, as the information 

 above given shows, onhj to a certain extent. The real reason 

 that wind is inimical to fog is that in a wind, or even gentle 

 breeze, the layers of air in contact with the earth's surface 

 move away before they have time to condense, and so in a 

 wind fog cannot Reformed. 



Another fact some of us have noted is that fog generally 

 occurs when the barometer is hiyh; and the higher the 

 barometer the worse may the fog be expected to be. We 

 have not, perhaps, all thought out the reason of this ; some 

 have stated that with a high barometer the atmosphere is in 

 an electrical condition, and this helps to generate a fog, but 

 there does not seem to be much in this theory. The simple 

 explanation is that a high barometer generally accompanies 

 anticyclonic conditions, and an anticyclone and calm weather 

 almost invariably go together ; while, as we have seen, calm 

 weather is the producer of fog. 



It may be well just to explain again what is the meaning of 

 the word " anticyclone." The atmosphere is constantly moving 

 in a series of waves forming part of gigantic circles ; high 

 pressure (or a high reading of the barometer) is found at the 

 crests of these waves ; low pressure in their hollows. When 

 the centre of these great circular waves is loicer than those 

 surrounding, the weather is cyclonic, and cyclonic weather is 

 generally changeable, with some wind and, in advance of the 

 lowest pressure, rain. When the centre is hie/her than the 

 surrounding waves, the weather is anticyclonic. Such it is at 

 the present time, and has been for the last fortnight, but the 

 centre has happily not remained in one place. It is now, 



