252 PROGNOSTICS OF THE WEATHER. 



When the mercury in tlie tube is fluctuating, unsettled weather may 

 be expected. A sudden rise in the barometer is no proof, at any time, 

 of a continuance of fair weather ; but in rainy and cloudy weather, 

 when the mercury is convex and continues slowly and continually rising 

 for two or three days successively, settled weather for nearly a week, 

 at least, may be expected ; or in fine weather, when the mercury, being 

 near 30 degrees, and concave, continues gradually to descend for some 

 days, rainy and stormy weather will soon follow. 



A current of air from the north, inclining either eastward or west- 

 ward, will produce a condensation of the atmosphere, and consequently 

 cause a rise in the barometer, and usually dry, cold, or cool weather, 

 according to the season. A southerly wind, either easterly or westerly, 

 especially the latter, will generally make the mercury in the tube 

 descend. A south -west wind seldom fails to produce rain when it 

 continues twenty- four hours in that quarter. 



In foggy weather, if the barometer remains stationary, and especially 

 if convex, and inclined to rise, and the fog dissipates as the sun 

 advances towards the meridan, fine weather will follow ; but otherwise 

 rain. A ground fog in the evening will almost always be followed by 

 fine weather next day. 



When the mercury in the barometer is concave, although it may have 

 risen in the night in consequence of a hoar frost, if the clouds in the 

 morning towards the east, about sunrise, are of a deep red colour, rain 

 will almost certainly follow ; and often in heavy showers in the course 

 of the day. 



If the wind is westerly, a rainbow in the morning indicates rain. 

 The barometer will then certainly descend ; and very often the ther- 

 mometer will be higher than the usual temperature of the season. 



But with the wind in the same quarter, especially when the western 

 clouds have a bright tinge of red, a rainbow in the evening towards 

 sunset, is almost a sure presage of fine weather the following day. 

 Hence the old proverb, that a rainbow at night is a shepherd's delight, 

 and a rainbow in the morning is a shepherd's warning. 



When it rains early in the day, with an easterly wind, it almost 

 always continues until towards noon ; but rather in misty or drizzling 

 rain than in heavy showers. If it does not then clear, it will not 

 entirely cease before sunset. 



The wind following the sun in his diurnal course, and a gentle breeze, 

 is a presage of fine, and generally of settled, weather. But if it backs 

 from the west towards the south, rain may be expected. 



