_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._
_Philadelphia, March 18, 1755._