PROGNOSTICS OF THE WEATHER. 253 



The barometer being concave, if the highest hills in the neighbourhood 

 in the morning are at the same time cloud-capt, and remain so till 

 afternoon, rain may be expected, But if the morning mist on the 

 summit of the hills gradually disappears towards noon, fair weather 

 will follow. Those who reside on plains, where there are no high hills 

 in sight, may judge of the weather by the smoke of their chimneys. If 

 it spreads abroad, and scarcely rises above the house, rain may be 

 expected in the course of the day. When it immediately descends 

 below the roof of the house, rain is almost certain ; but when the air is 

 in a condensed state, the smoke will rise rapidly, and perpendicularly, 

 if not immediately dispersed by the wind. It is sometimes unadvisedly 

 said that the air is heavy, and drives down the smoke ; but the fact is 

 precisely otherwise, for when the atmosphere is most condensed, it 

 immediately absorbs the smoke, as it does all other vapours and exha- 

 lations. Whence a condensed state of the atmosphere, which raises the 

 barometer, produces fair weather ; and the contrary high wind, and 

 rain, or both. 



It is recommended to every person who wishes to consult the baro- 

 meter, to learn to read the height of the mercury by the degrees, and 

 not by the words now engraved on the plate ; otherwise the instrument 

 maker would do well to engrave the words on the plate according to the 

 height of the place from the level of the sea, where the instrument is 

 to be used ; for in situations very much elevated, the mercury will be 

 much lower than in valleys, and, besides, it frequently rains from the 

 causes above-mentioned, when the mercury, in common instruments, is 

 at fair, and sometimes even near set fair ; and, on the contrary, the 

 weather frequently continues settled, when the mercury remains 

 stationary at changeable. The principles of the barometer being thus 

 misunderstood, has greatly depreciated the value of this excellent 

 instrument, and made many persons hastily pronounce it to be perfectly 

 useless, as what is commonly called a weather-glass. 



When the barometer rises as the tides increase, especially in summer, 

 settled weather may be expected. When, on the contrary, at the same 

 season, the barometer falls with the increase of the tides, wet or variable 

 weather will soon follow. So likewise, when the mercury rises, and 

 continues convex with the fall of the tide, settled weather may be 

 expected ; but when the mercury is concave, and continues descending, 

 on the decrease of the tide, rainy or squally weather will soon follow. 

 As a general remark on the subject of the influence of the tides on the 

 atmosphere it may once more be observed, that the principal changes 



