88 Sheet Lightning. 



the heavens were peculiarly calm and serene. Nevertheless, 

 when he cast his eye towards Geneva, he perceived in the 

 horizon several bands of clouds whence flashes of lightning 

 issued, without, however, any attending thunder. During 

 the same night, and at the same instant, the towtr of Ge- 

 neva was visited by one of the most tremendous thunder- 

 storms it had ever witnessed. Again, on the 31st of July 

 1813, Mr L. Howard perceived at Tottenham, near London, 

 some trifling flashes of sheet lightnings in the distant hori- 

 zon towards the south-east. The sky was bespangled with 

 stars, and not a cloud was to be seen in the firmament. Soon 

 after this, Mr Howard learned from his brother, at the time in 

 the south-east corner of England, that on that same 31st of 

 July, at the very time the silent lightnings were perceived at 

 Tottenham, there raged at Hastings a dreadful storm, which 

 also extended over France, as far as from Dunkirk to Calais. 

 Thus, the flashes which were noticed in the atmosphere of Lon- 

 don were produced in the midst of clouds situated nearly fif:v 

 Jeagues off. 



But the proving that sheet lightning is sometimes nothing 

 more than reflected lightning, does not establish that it has 

 always this origin. Those who believe that a sky which is per- 

 fectly serene is often striated with direct spontaneous flashes, 

 proceeding from an atmosphere devoid of clouds, may support 

 their opinion by the circumstance that sheet lightning often ex- 

 hibits itself, as for example at Paris, throughout whole nights, 

 and in every quarter of the horizon, without any part of the sky 

 becoming obscure. At the same time, however, it must be al- 

 lowed that the prolonged existence of a sort of Oasis of serenity 

 seems not very probable. So soon as the time arrives, that 

 there are as many observers scattered over the face of a coun- 

 try as Meteorology requires, then we shall easily ascertain, by 

 the comparison of their several journals, whether the sheet 

 lightning which is seen in any given spot, is derived from the 

 reverberation of the flashes of a distant storm, or is not so. 

 Even before the arrival, however, of that happy period, it 

 seems to me possible to decide the question by observations 

 taken at a single place, by a single individual, and even at the 

 very instant the phenomenon is observed. 



