Hypothesis, of the sea being the grand source of lightning,
retracted.--Positive, and sometimes negative, electricity of the
clouds discovered.--New experiments and conjectures in support of
this discovery.--Observations recommended for ascertaining the
direction of the electric fluid.--Size of rods for conductors to
buildings.--Appearance of a thunder-cloud described. 269
Additional proofs of the positive and negative state of electricity
in the clouds.--New method of ascertaining it. 284
Electrical experiments, with an attempt to account for their
several phenomena, &c. 286
Experiments made in pursuance of those made by Mr. Canton, dated
December 6, 1753; with explanations, by Mr. Benjamin Franklin. 294
Turkey killed by electricity.--Effect of a shock on the operator
in making the experiment. 299
Differences in the qualities of glass.--Account of Domien, an
electrician and traveller.--Conjectures respecting the pores of
glass.--Origin of the author's idea of drawing down lightning.--No
satisfactory hypothesis respecting the manner in which clouds
become electrified.--Six men knocked down at once by an electrical
shock.--Reflections on the spirit of invention. 301
Beccaria's work on electricity.--Sentiments of Franklin on pointed
rods, not fully understood in Europe.--Effect of lightning on the
church of Newbury, in New England.--Remarks on the subject. 309