"The Radium Seekers" is a fiction story about our hero and his friends going to South America to look for radium, which has anti-gravity properties, and then battle with a race of cruel Inca-type people who use the radium to fly, and disguise themselves as giant birds and terrorize the locals.
Francis Henry "Frank" Atkins (18471927) was a British writer of "pulp fiction", in particular science fiction aimed at younger readers. He wrote under the pseudonyms Frank Aubrey and Fenton Ash.