This note presents new evidence concerning the existence of a Draft Letter written by John Walsh MP FRS, describing the generation of an electric spark from Gymnotus electricus, submitted for publication to the President of the Royal Society Sir John Pringle in the summer of 1777. It confirms Walsh's intention to publish a description of his spark experiments plus his observations of the eels' mysterious "electrical sense". For reasons that have never been understood, Walsh failed to publish a formal account of the Gymnotus spark generation, despite its perceived importance.