Account of a 'Thunder-ftorm in Scotland. 149 
tf forty or fifty feet afunder ; and, if they were to be at Bill 
“ Imaller chfhnces afunder, the fecurity they would afford 
46 would be {fill more perfect.” 
The reafon of this precaution is fully explained in many 
parts of the above-mentioned Treatife, particularly in feftion 
423*; and the circumftance, very worthy of obiervation, 
related by Mr. Brydone, namely, that the diftance was only 
“ about twenty four yards," between Lauder, who was killed, 
and his companion, who 64 was fenfible of no fhock, nor un- 
“ common fen fat ion,” does clearly demonftrate the propriety 
of this precaution, of erecting fcvcyal f conducting rods upon 
an extenfive building. 
This information muff be particularly interefling to the 
Board of Ordnance, on account of the fecurity of their ma- 
gazines, particularly their powder magazines at Purfleet. The 
* See nlfo Part XVIII. of my Principles of Electricity (from § 494 to § 518 
inclufively), where I have clearly demonltrated this proportion, namely, that, 
44 high and pointed metallic conductors [when properly conftruCted, and when made to 
6i communicate completely with the common flock] tend not only to prevent 
44 a main Jtroke of lightning and the lateral cxplofion ; but tend likewife moll power- 
41 fully to prevent any dangerous eleftrical returnbig firoke whatever from taking 
“ place near that part of the edifice upon which they are ereCted. So admirable,. 
41 and fo extenfive, is the principle upon which is founded this fimple and molt 
44 incomparable invention !” 
4 See alfo (in the volume LXVIII. of the Philofophical TranfaCtions, part I. 
p. 313. et feq.) the “ Report of the Committee, appointed by the Royal Society, 
600 
44 to conlider of the moll effectual Method of fecuring the Powder Magazines at 
“ Purfleet againft the Effects cf Lightning, in compliance with the Requeft of the 
44 Board of Ordnance;” in which Report, feveral high and acutely-pointed con- 
ductors, properly connected with the bottom of the wells, are propofed to be 
<rcCted ; and other precautions, founded on a like principle, are recommended. 
r fecurity,. 
