from the Report of the Commit tee. See, 817 
prefervatives from lightning. And here it is neceffary to 
obferve, that buildings may be expofed to a ftroke of 
lightning in feveral different ways. The lightning 
which, to avoid prolixity, I fhall only fpeak of as pofitive 
electricity : the lightning, I fay, may accumulate direCtly 
over the building; or it may be brought towards the 
building by a fmall cloud fetching it in feveral fucceffive 
trips from a large cloud at fome diftance; or a large elec- 
trified cloud may be carried rapidly towards it by the 
wind : a circumftance this by no means rare, there being 
no lefs than four inftances of it upon record in the Phil. 
Tranf. vol. xlix. p. 16. and p. 309. vol. lxi. p. 72. 
and vol. lxiv. p. 351. In the firft of thefe fuppofed 
cafes a fharp-pointed conductor might poffibly drain the 
cloud of its lightning as fail as it began to accumulate, 
and thereby prevent any explofion whatever. In the 
fecond, as the cloud, by fuppofition, not being driven in 
one direction by the wind, could not move with any re* 
markable velocity, it is reafonable to imagine, that in 
this cafe alfo there might be no explofion ; and that the 
electricity of the larger cloud might be gradually ex-^ 
haufted. But if, according to the third fuppofition, a 
cloud of great extent and highly electrified fhoukl be 
driven with great velocity in fuch a direction, fo as to 
pafs direCtly over the fharp-pointed conductor, there can 
Vol. LXVIII. 5 I be 
