An Extract of a Letter from James Logan, Esq; To Sir Hans Sloane, Bart. R. S. Pr. concerning the Crooked and Angular Appearance of the Streaks, or Darts of Light'ning in Thunder-Storms

VI. An Extract of a Letter from James Logan, Esq; to Sir Hans Sloane, Bart. R. S. Pr. concerning the crooked and angular Appearance of the Streaks, or Darts of Lightning in Thunder-Storms. Philadelphia, Sept. 20, 1735. I shall crave thy Indulgence further to add, that looking into the Second Volume of that ingenious Gentleman Stephen Hales's Staticks, of which I have lately happened to have a cursory View, I observed him to mention that Phenomenon of the Streaks or Darts of Lightning in Thunder-Storms appearing crooked and angular (I do not remember his Words) as a thing not yet accounted for; and therefore he guessed at a Solution of it*. The Clouds are generally distinct Collections of Vapours like Fleeces, and therefore the Rays of Light thro' them must pass thro' very different Densities, and accordingly suffer very great Refractions: From thence therefore, undoubtedly, that Appearance must arise. For it is most highly absurd to imagine, that Fire darted with such a Rapidity, can from any assignable Cause deviate in Fact from a Right Line, in the Manner it appears to us. And this, if duely considered, may probably be found a plenary Solution. * See Steph. Hales's Statical Essays Vol. 2d. p. 291: Obser.