and on certain correlative V hcenomena. 343 



Barbadoes at noon of this memorable day was involved in 

 midnight darkness, and the whole surface of the island was 

 covered with the dust or cinders : of this substance I have a 

 specimen which fell upon the deck and sails of a vessel, 150 

 miles to windward of the volcano. In this case it is probable 

 that a continued succession of ignited materials being pro- 

 jected from the mountain and rarefying the air, an upward 

 draught was established, which carried the volcanic dust into 

 the higher regions of the atmosphere, whence it was wafted 

 by upper currents and fell over a vast space around. With 

 these phagnomena history affords no parallel instance; al- 

 though it is mentioned by Pliny, that the explosions of iEtna 

 had been heard, and its cinders thrown upon the African coast. 

 But to resume the consideration of ' heat lightning.' 



When reflected lightning only can be seen, darting from 

 below the horizon, we have no means of forming an estimate 

 of the distance of thunder-storms. We shall perceive the flash 

 or reflected light when the electric stream itself is developed 

 far below the horizon ; it is not strange, therefore, that we so 

 often see the flash without hearing the explosion. 



Were observations made for this purpose in countries well 

 inhabited and of considerable extent, as France, Germany, &c, 

 an estimate might be formed of the place of distant thunder- 

 storms and great rains, or of those at least which happen at 

 night. Such observations would, perhaps, effect much lor the 

 advancement of meteorological knowledge ; and thus, I pre- 

 sume, those meteors which are vaguely regarded as silent 

 electrical emanations, would be found to proceed from real 

 thunder-storms, in France engendered about the Pyrenees 

 especially, and in North America from the Alleghany moun- 

 tains : that such is the case I feel persuaded, at least with 

 respect to the equatorial regions. By observing the direc- 

 tion of those flitting lights, and by subsequent inquiry at 

 places falling under the same rhumb, we might often he en- 

 abled to trace out the localities of those mysterious Jircs of 

 the horizon. This remark regards the observations requisite 

 for finding the place of heat lightning, so called, properly re- 

 flected lightning, as I presume. 



Since this subject was laid before the Philosophical Society 

 (of British Guiana), I have been enabled to obtain such infor- 

 mation iroin intelligent persons residing far up the Demerara 

 River (near the lalls and mountainous regions) as seems to place 

 the matter altogether beyond a doubt; especially from Mr. For- 

 syth, who lives near the falls, and Mr. Patcrson (of Christians* 

 burgh), a gentleman of probity and correct observation. Ac- 

 cording to their testimony, the great rains (about June and 



