a Thunder-storm as observed at Woolwich. 421 



bition. I walked to the top of Wellington-street, from which 

 place I had an exceedingly fine view of the storm, now too 

 distant to hear even a feeble murmur of those thunders, 

 which, I am persuaded I may safely affirm, were to the in- 

 habitants immediately in their vicinity terrible to an unusual 

 degree. 



It was now 9 o'clock, and the lightning was magnificent 

 indeed. Nature appeared as if disposed to gratify the utmost 

 extent of curiosity by an unremitting display of her electrical 

 elemental fire. 



For about half an hour the storm appeared to be nearly 

 stationary, hovering over a tract of low land on the Essex 

 and Kent sides of the Thames, perhaps not far from Purfleet. 

 The lightning was unusually refulgent; the flashes in rapid 

 succession, and discharged in every possible direction that 

 can be imagined, and, generally through a longer striking 

 distance than I had ever before noticed. Three or four dis- 

 charges which occurred a little after 9 o'clock, darted through 

 a horizontal arch of about 50° each ; and several of those 

 which were directed vertically and oblique to the horizon, 

 shot through 30° or 40°, the fluid being visible in every part 

 of the circuit. 



If this lightning was discharged over Purfleet, or there- 

 abouts, as I have supposed, it would be about eight miles 

 from where I was standing. Now allowing seven miles to be 

 the mean distance of the lightning discharged in a track at 

 right angles to the line of sight, the angle of 50° would 

 give a chord of nearly six miles and a half for the striking 

 distance, or the tract of air through which the lightning tra- 

 velled visibly at one discharge. The apparently vertical and 

 oblique discharges were much nearer in some part of the cir- 

 cuits than those which shot through the extraordinary hori- 

 zontal ranges. The rain, I imagine, was falling in torrents, 

 which would greatly facilitate the transmission through long 

 striking distances. Moreover, the inferior density of the air 

 in the regions of the clouds, and the thin aqueous vapours 

 which are floating there, tend very much to facilitate the trans- 

 mission. 



Buildings, trees, and other tall objects are not usually 

 struck by lightning before the falling of rain, the dry dense 

 air offering too great a resistance to be transpierced from the 

 clouds to the ground. 



From the time that the clouds arrived within the influence 

 of the Thames, they seemed to travel nearly in its direction ; 

 for although the lightning played over some miles of country 

 on both sides of its banks, the river appeared to be the direc- 



