186 BEST'S ART OF ANGLING. 



descent of the Barometer indicates principally 

 violent wind. 



The Thermometer also, which measures the 

 degree of heat in the air near the earth, will 

 contribute towards denoting when changes are 

 likely to take place in the lower regions of the 

 atmosphere : The Hygrometer distinguishes the 

 quantity of moisture in the atmospheVe, and the 

 Electrometer will point out the quantity of 

 Electricity which prevails in it. 



The words generally engraven on the platen 

 of the Barometer, serve rather to mislead thajri 

 inform ; for the changes of the weather depend 

 rather on the rising or the fallingof the mercury ? 

 than of its standing at any particular height. 



When the mercury is as high as fair, oi^at 30 

 degrees, and the surface of it is concave, begin- 

 ning to descend, it very often rains ; and on the 

 contrary when even the mercury is at 29 degrees,, 

 opposite to rain, when the surface of it is con- 

 vex, beginning to rise, fair weather may be ex- 

 pected: these circumstances not being known, 

 or not being duly attended to, is the principal 

 cause that farmers and others have not a pro- 

 per confidence in this instrument. 



It must be observed that, cateris paribus, the 

 mercury is higher in cold, than in warm weather, 

 and commonly early in the morning, or late iu 

 the evening, then at noon, which seems occa* 

 sioned by the obvious causes of the atmosphere 

 being condensed by the cold of the night, and 

 rarefied by the heat of the day. 



The following observations deserve attention* 



1. The least alterations in the mercury are to 

 be observed (especially in a showery time). 



2. The rising of the mercury, presages, ia 

 general, fair weather, and its. falling, fowl. 



