1907 F. Harms Dielectric coated transmission line 1950 George J. Goubau Dielectric coated transmission line 1899 Arnold Sommerfeld did work on surface waves from wires 1909 johann Zennik while working to explain Marconi's trans-oceanic results, showed that a unique type of surface wave could travel along the interface between the ground and the air (In the words of James Corum) 1916 Nikola Tesla cited the analysis of mathematician Arnold N. Sommerfeld as verification of his explanations of observed radio phenomena. Tesla was referring to his wireless system in which, he claimed, 90% to 95% of the electrical energy was manifested at the transmitters output as "current waves" with the remainder existing as dissipating electromagnetic radiation (In the words of James Corum) 1916 “This coil, which I have subsequently shown in my patents Nos. 645,576 and 649,621, in the form of a spiral, was, as you see in the form of a cone.”