344 Dr. J. Hancock's Observations on 'Heat Lightning,' 



July) are there ushered in by the most tremendous peals of 

 thunder and vivid lightning, by which large trees are often 

 shattered to pieces. The same is further corroborated by the 

 testimony of the Indian natives*, who (in light canoes) pass 

 in a few hours from the high lands enveloped in thunder- 

 storms to a serene air on the coast where no signs of the storm 

 appear, except at night, in those silent flashes which dart from 

 below the horizon in the direction of the mountains. 



On the flat coast of Guiana thunder-storms are compara- 

 tively rare. It is the more elevated summits, as the chain of 

 granitic mountains, which produce these extraordinary me- 

 teoric phenomena, furnishing, as it were, electrical magazines, 

 which, for certain periods of the year, render it the region of 

 incessant thunder-storms and impetuous rains. Thus, too, 

 the elevated ridge of the Isthmus of Darien, attracting the elec- 

 tricity from both oceans, is so remarkable for torrents of rain 

 and unequalled tempests of thunder and lightning; as at Porto 

 Bello and other parts of this chain. 



I trust that the foregoing considerations may serve to prove 

 that the phenomena which go under the vague names of 

 heat lightning, feux d'horizon, &c, being regarded as phos- 

 phorescences, ig?ies Jatui, or some silent form of electricity, 

 are no other than reflected lightning from distant thunder- 

 storms. It should be recollected, too, that they are seldom 

 observed during the dry season in the interior, between Sep- 

 tember and March. It is not generally considered that the 

 driest season on the coast is often contemporaneous with great 

 rains amongst the interior mountains; that here the rains com- 

 mence ; and that when the plains also become the theatre of 

 rains, and veiled in clouds, those distant and faint illumina- 

 tions are now rendered invisible by the density of the horizon. 

 The small distance at which thunder is audible, and the vast 

 space over which the electric fluid, in reflected gleams, be- 



* The vast tract, only known by the name of Interior Guiana, forms one 

 of the most interesting portions of South America. Those countries bor- 

 dering on the north, the south and west, as Mexico, Brazil, Peru, &c.,have 

 been more or less explored by European travellers, but Guiana remains a 

 real terra incognita. The writer has traversed some part of it, having been 

 deputed by the Colonial Government in 1810, on an embassy amongst the 

 interior tribes inhabiting the Essequibo, the Parime, the fabled El Dorado, 

 and North Brazil, in an expedition most summary and ill planned: he was 

 able to do little more than take a draught of the route and to mark a few 

 of the more interesting features of the country. Having resided, however, 

 nearly 25 years in the British Colonies and Spanish America, and made 

 numerous excursions inland, he can aver that a hundredth part of the 

 amount so liberally bestowed by the British Government for the discovery 

 of a North-west passage would, if laid out in exploring Guiana, be produc- 

 tive of far greater benefit to science and to the interests of the nation. 



