Chapter I: is a fair resumé of what is known of the electricity evolved

by the friction of wet steam against solids in the hydro-electric machine. He agrees with Faraday that the cause of the evolution of electricity by the liberation of confined steam, is not evaporation, but the friction of the water particles against the sides of the jet-piece or orifice. Pure gases do not excite electricity; but impure air, when compressed does, from the friction against the orifice of those particles of water which are suddenly condensed by the cooling influence of the expanding air.