276 Application of Barometer for indicating the Weather, 



fidently expected : — the same rule applies for predicting the 

 weather from evening till morning. 



8. During the increase of the moon there seems to be 

 a greater disposition or effort in the air for clear dry weather 

 than in the wain,: but this disposition does not usually 

 commence till about three or four days alter the new moon, 

 and ceases about three or four days after the full moon. 



9. The barometer should be observed occasionally thrice 

 in the day, or oftener when the weather is changeable, in 

 order to notice whether the mercury be stationary, rising, 

 or sinking; for from this circumstance, together with the 

 direction of the wind and the apparent state of the air at the 

 time, is information to be collected, and a continuance of the 

 same, or a sudden change of the weather, to be foreseen*. 



10. Lastly, Observe always — The higher the mercury 

 shall stand in the scale in each instance, and the more re- 

 gularly progressive its motion shall be, the stronger will be 

 the indication : likewise, The more the wind inclines towards 

 the north or east points, the greater will be the disposition 

 in the air for fair weather. 



The indications of rainy lueather will obviously be the 

 direct reverse of those rules which predict fair weather. 



Frost is indicated in winter by the same rules that in- 

 dicate fair weather, the wind being in or about the north 

 or east points, and the thermometer sinking towards 32. 



A fall of snow seldom comes without a previous frost of 

 come duration, and is indicated by the sinking of the baro- 

 meter, especially if the mercury be below changeable, 

 and the thermometer at or near the freezing point. 



When the temperature of the air is about 35°, snow and 

 rain sometimes fall together; at a warmer temperature than 

 35° it seldom snows, or rains at a colder temperature. 



Thunder is presaged by the same rules which indicate rain, 

 accompanied bv sultry heat ; the thermometer being up to 75. 



Storms, hurricanes, and high winds, are indicated by the 

 barometer falling suddenly, or sinking considerably below 



MVCll KAIX. 



The barometer is known to be rising or sinking by the 

 mercury having either a convex or concave surface, or by 

 the perceptible rise or descent of the mercury if at the time 

 of observation the barometer be gently rapped f. 



if at any time the weather should differ widely from the 



* A barometer, conveniently portable, merely for the purpose of ascer- 

 taining whether 1 the atmosphere U beconrng denser or rarer, is a great desi- 

 derafum, hut, 1 should apprehend, not very easy to be constructed. 



f The best index for these observations is a plate of metal extending as 

 far as the middle of the column of mercury iu the barometer, having a 

 0<*ff4f><g line acres.; [I s ceatre of the plate. 



indications 



