application of Barometer for indicating the Weather, 275 



are subtracted by the air, and that in this case the spectra 

 and the irises ought to present a single colour only, which 

 is the red. 



LI 1 1. On the Application of the Barometer for indicating 

 the Weather , and for measuring of Heights in the AtmO" 

 sphere. By Richard Walker, Esq, 



To Mr, Tilloch, 



Sir, In order to prognosticate the weather by means of the 

 barometer, one general rule should be premised, viz. that, pre- 

 viously to observing the barometer, the state of the weather 

 at the time should be accurately noticed in every particular. 

 Hence, to speak figuratively, we might affix this motto to 

 the barometer, " Tell me what the weather is, and I will 

 tell you what it will be." 



The circumstances to be collected previously to inspect- 

 ing the barometer are, 1st, The state of the atmosphere, 

 respecting its degree of clearness or cloudiness : 2dly, The 

 direction of the wind, together with its steadiness or varia- 

 bleness: and 3dly, The altitude and density of the clouds. 



Signs of Fair Weather, 



1. The barometer rising may be considered as a general 

 indication that the weather, comparatively with the state of 

 it at the time of observation, is becoming clearer. 



2. The atmosphere apparently becoming clearer, and the 

 barometer above rain, and rising, show a disposition in the 

 air for fair weather.* 



3. The atmosphere becoming clear, and the barometer 

 above changeable, and rising, indicate fair weather. 



4. The atmosphere clear, and the barometer near fair, 

 and rising, denote continued fair weather. 



5. Our prognostic of the weather is to be guided, rela- 

 tively, thus : If, notwithstanding the sinking of the baro- 

 meter, little or no rain follow, and it afterwards rise, we 

 may expect continued dry weather. 



6. If, during a series of cloudy rainy weather, the baro- 

 meter rise gradually, though yet below rain, especially if 

 the wind change from the south or west towards the north 

 or east points, clear and dry weather mav be expected. 



7. The weather for a short period, viz. from morning 

 until evening, may commonly be foretold with a considera- 

 ble degree of certainty. If the barometer has risen during 

 the night and is still rising, the clouds are high and ap- 

 parently dispersing, and the wind calm, especially if it be 

 in or about the north or east points, a dry day may be con- 



S 2 fidently 



