Tom Swift and His Electronic Retroscope (The New Tom Swift Jr. Adventures #14) by Appleton, Victor II - 1962

"Enraged Jaguars, violent winds of hurricane force, and a mysterious 'giant' who roams the jungle around the Mayan village in Yucatan, Mexico, where Tom is encamped, are only a few of the perils that the young inventor encounters during his thrilling expedition.
"But even more feared by the young inventor is an unknown saboteur, intent on destroying Tom's two latest inventions--the electronic retroscope camera and his "parachute" plane, designed for landing in small areas.
"Undaunted by the hazards that surround him and assisted by teh friendly natives, Tom perseveres in his objectives. He tests his paraplane for landing maneuverability in densely grown jungle areas, and uses his retroscope (magic to the natives! ) to restore--photographically--ancient carvings and writing on old Mayan relics. Tom is astounded when he discovers that some of the carved symbols are similar to the mathematical symbols used by his mysterious friends in outer space to communicate with him.
"Is it possible, Tom wonders, that beings from another planet actually landed in Yucatan centuries ago?
"What happens to Tom and his friends as they seek the answer to this question in the dark depths of a buried temple will hold every reader in gripping suspense to the last line of this challenging adventure "
Age Level: Grades 4-10 .