TO W. GARNETT, Esq. 
                                                                     Glenlair, 4th January 1877

By all means take the Groves and coils for your lecture. Are you aware that the electric flash is entirely due to the    resinous particles of electricity? This is well known on the stage, where they blow the particles through a tube over    a candle to make stage lightning. The vitreous electricity has nothing to do with it, as you may prove by using   pounded glass.