80 METEOROLOGICAL 



<!^lb0erbation0 



THUNDER STORMS AND LUMINOUS METEORS. 



Intimately connected with the state of the 

 aqueous vapour in the atmosphere, are the elec- 

 trical phenomena of thunder and lightning. By 

 evaporation the electric fluid is silently raised 

 and accumulated in the air, and by condensa- 

 tion, or the conversion of steam into v\^ater, its 

 intensity is increased ; till, under favourable cir- 

 cumstances, it manifests itself in those energetic 

 and sublime displays which are witnessed in 

 thunder storms. From the annexed comparative 

 view, founded on the experience of the five years, 

 commencing with 1821, and terminating with 

 1825, it is plain, that those months in which the 

 dew-point is highest are most liable to thunder 

 and lightning. 



Mean Monthly Point of Deposition. 



Jan. Feb. Mar. April. May. June. 



340.2 35°.l 36*^.9 40°.4 44°.7 49°.6 



Jfumher of Thunder Storms observed. 

 4 10 15 16 



