PNEUMATICS. 151 



thunder. 3. In winter, the rising presages frost ; 

 and, in frosty weather, if the mercury fall three or 

 four divisions, there will probably follow a thaw; 

 but in a continued frost, if the mercury rise, it 

 will most likely snow. 4. When foul weather 

 happens soon after the falling of the mercury, ex- 

 pect but little of it ; and, on the contrary, expect 

 but little fair weather, when it proves fair shortly 

 after the mercury has risen. 5. In foul weather, 

 when the mercury rises much and high, and so 

 continues for two or three days before the foul 

 weather is quite over, then expect a continuance 

 of fair weather to follow. 6. In fair weather, 

 when the mercury falls much and low, and thus 

 continues for two or three days before the rain 

 comes, then expect a great deal of wet, and pro- 

 bably high winds. 7« The unsettled motion of 

 the mercury denotes uncertain and changeable 

 weather. 8. You are not so strictly to observe 

 the words engraved on the plates (though in 

 general it will agree with them) as the mercury's 

 rising and falling ; for if it stand at much rain, 

 and then rise up to changeable, it presages fair 

 weather, though not to continue so long as if the 

 mercury had risen higher; and so, on the contrary, 

 if the mercury stood sxtjair, and fall to changeable, 

 it presages foul Weather ; though not so much of 

 it as if it had sunk lower. 



From these observations, it appears that it is not 

 so much the height of the mercury in the tube that 

 indicates the state of weather, as the motion of it 

 up and down. 



Besides the barometer, there are several other 

 instruments used for meteorological purposes; such 

 as the thermometer, hygrometer, wind-gage, rain- 

 gage, and electrometer. 



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