and on certain correlative Phenomena. 341 



those of Barcelona, Chaymas, and Calaboso. Soon after this 

 the rivers begin to swell, and the rains commence in the 

 Lower Orinoko, where, conversing upon this subject, I was 

 told by one, it was relampago sin trueno; by another, una 

 Jantasma ; a learned friar very gravely pronounced it to be 

 la madre de trueno. I inquired of several, whether it was not 

 attended with thunder? O, never; it was relampago, no mas t 

 ' lightning only.' Why so? had they ever been involved in it, 

 or seen it close to them ? Never ; it was always seen far off, 

 1 muy lexos\ This answer almost confirmed me in the con- 

 verse opinion to theirs, and I have since fully satisfied myself 

 on that head. These appearances occur more or less every 

 year, but were especially remarkable in Essequibo, at the 

 end of May and beginning of June 1819, and were followed 

 soon after by great thunder-storms on the coast ; and I have 

 ever since regarded these corruscations, not merely as the 

 precursors, but as announcing the actual commencement of 

 great rains and thunder-storms in the interior, such in fact as 

 I had experienced in travelling there at the same season in 

 1811. 



The same phenomenon is, in North America, called heat 

 lightning, as I believe it is in Europe— -feux d'horizon of the 

 French. Without considering the great distance at which 

 lightning is perceived and the small distance that thunder is 

 heard, it is believed that such flashes are not accompanied by 

 thunder or any explosion. As it occurs chiefly in hot weather, 

 it is called heat lightning, Jires of the horizon, and commonly 

 regarded as some anomalous meteors, or electrical emanations 

 unattended by thunder. At the same time, it is not merely a 

 vulgar fancy, but one which has been entertained by the 

 learned of all ages, and I am surprised to find it subscribed 

 to by such distinguished travellers as Humboldt and Volney. 



" At Arragua," says M. Humboldt, " in the beginning of 

 the month of March, the accumulation of the vesicular va- 

 pours, visible to the eye, and with them, signs of atmospheric 

 electricity augmented daily. We saw flashes of heat lightning 

 to the south : and the electrometer of Volta displayed con- 

 stantly at sun-set vitreous electricity." — Pers. Narr. vol. iv. 

 p. 402. "On the morning of April 15th (Upper Orinoco) 

 the sky was in a great part obscured, and lightnings furrowed 

 thick clouds at more than 40° of elevation. We were sur- 

 prised at not hearing the sound of thunder. Was it on account 

 of the prodigious height of the storm? It appears to us, that 

 in Europe the electric flashes without thunder, vaguely called 

 heat lightning, are seen generally nearer the horizon." — Persl 

 Narr. vol. V. p. 8. 



