Regular clincher tires cut from the bead and glued onto solid rubber cores.
His name is Jonathan Summerfield, or Joff, and he's as interesting as you'd expect. His website is of course Penny Farthing World Tour. His itinerary to date reads as such here. Joff was on this leg when he passed through Salida, and the next section to Kansas is recorded here. He's somewhere near Virginia/Maryland at this point, if not further. His pictures are excellent, the ride must be amazing. His Penny Farthing (the difference in wheel size is likened to the difference in a penny and farthing coin) is fixed: if the wheels turn, the cranks turn. An upright position, a certain learning curve, but there's no doubt he knows what he's doing, on a bike he built himself. He told me about crossing Himalayan passes, chatting with the airlines (for oceanic flights) about stowing his bike away, and all in all, clearly having a very good time.