Edmond Hamilton 
Captain Future #5: The Seven Space Stones [EPUB ebook] 

Curt Newton, spacefarer, and the Futuremen take off on the most thrilling treasure-hunt of all time in quest of the Solar System’s greatest prize!
The Captain Future saga follows the super-science pulp hero Curt Newton, along with his companions, The Futuremen: Grag the giant robot, Otho the android, and Simon Wright the living brain in a box. Together, they travel the solar system in series of classic pulp adventures, many of which written by the author of The Legion of Super-Heroes, Edmond Hamilton.