C 202 ] 
pliers, and have given them room to hope, that what 
they have learned before in their mufeums, they may 
apply, with more propriety than they hitherto could 
have done, in illuftrating the nature and effects of 
thunder ; a phenomenon hitherto almoft inacceflible 
to their inquiries. 
But to make the mod: certain advantage of thefe 
new difcoveries, we fhould confine ourfelves to fadts ; 
and if we do draw confequences from them, they 
fhould be immediate and neceflary ones ; for, when- 
ever our difcoveries feem to promife to be ufeful and 
important, we are apt to hope and expect great fuc- 
cefs from them : we mud: therefore be careful to re- 
frain our imagination, or we fhall fall into error. 
Thefe confiderations have induced our author to 
examine with care, what may truly be concluded 
from the experiments propofed by Mr. Franklin of 
Philadelphia, and fince carried into execution in- 
France, and elfewhere, in relation to the electricity 
of the clouds during a form ; by weighing every cir- 
cumftance, and comparing the greatnefs of the ef- 
fects, which have been had in view, with the more 
than apparent infufficiency of the means, which have 
been employed to produce them. He thinks, he fees 
clearly, that the confidering the electrifation of pointed 
bodies as a proof of ledening the matter of thunder, 
is abufing a real difcovery to flatter ourfelves with a 
vain hope ; and it is chiefly to diflipate this error, if 
it yet fubfifts, that determined our author to print, 
in the work before us, fome reflexions, which he had 
made at fiid only for himfelf, and a few perfons, to 
whom he was defirous of communicating his opinion. 
Mr. 
