What happens to the Time Traveler when he tries to get behind the bronze panels?

I'm not sure what you mean. The Time Traveler is not successful in getting behind the panels, though, he is frustrated. He also discivers some type of ventilation system in this chapter but is unable to investigate. The one thing the TT does discover is an inscribed date, "Well, on the third day of my visit, that was how the world of Eight Hundred and Two Thousand Seven Hundred and One presented itself to me!"