176 PROGRESS OF ATMOSPHERIC 



lightning were seen in the south, and at sunset Vol- 

 ta's electrometer regularly displayed positive indi- 

 cations, the separation of the pith-balls being from 

 three to four lines. After the 26th of the latter 

 month, the electrical equilibrium of the atmosphere 

 seemed broken, although the hygrometer still de- 

 noted great dryness. 



The following is an account of the atmospheric 

 phenomena in the inland districts to the east of the 

 cordilleras of Merida and New-Grenada, in the lla- 

 nos of Venezuela, and the Rio Meta, from the fourth to 

 the tenth degree of north latitude, wherever the rains 

 continue from May to October, and consequently in- 

 clude the period of the greatest heat, which is in 

 July and August : — " Nothing can equal the purity of 

 the atmosphere from December to February. The 

 sky is then constantly without clouds, and should 

 one appear, it is a phenomenon that occupies all the 

 attention of the inhabitants. The breeze from the 

 east and north-east blows with violence. As it 

 always carries with it air of the same temperature, 

 the vapours cannot become visible through refrigera- 

 tion. Towards the end of February and the begin- 

 ning of March the*blue of the sky is less intense ; 

 the hygrometer gradually indicates greater humid- 

 ity; the stars are sometimes veiled by a thin stratum 

 of vapours ; their light ceases to be tranquil and 

 planetary ; and they are seen to sparkle from time 

 to time at the height of 20° above the horizon. At 

 this period the breeze diminishes in strength, and be- 

 comes less regular, being more frequently inter- 

 rupted by dead calms. Clouds accumulate towards 

 the south-east, appearing like distant mountains 

 with distinct outlines. From time to time they are 

 seen to separate from the horizon, and traverse the 

 celestial vault with a rapidity which has no cor- 

 respondence with the feebleness of the wind t>at 

 prevails in the lower strata of the air. At the end 

 of March the southern region of the atmosphere is 



