From May and June of 1935.

The Secret In The Sky

A ball of fire streaks across the heavens leaving death and ruin in its wake -- A machine of terror which cannot be halted -- An amazing intelligence capable of rendering an entire continent barren... All America trembles as Doc Savage grapples with the most awesome challenge of his astonishing career!

The Roar Devil

The Roar Devil -- he shook the earth. He stopped all sound. He had a vast organization of desperate criminals at his command. Now the good citizens of Powertown were terrorized. At any moment the Roar Devil might strike again. They sent for the only person whose cunning and skill could defeat him -- the Man of Bronze.