A man placed a US patent on his "Hollow Earth Theory" Model
Marshall Gardner wrote A Journey to the Earth's Interior in 1913 and published an expanded edition in 1920. He placed an interior sun in the Earth and built a working model of the hollow Earth which patented (U.S. Patent 1,096,102). Gardner made no mention of Reed, but did criticize Symmes for his ideas. About the same time Vladimir Obruchev wrote a novel Plutonia, in which the hollow Earth possessed an inner sun and was inhabited by prehistoric species. The interior was connected with the surface by an opening in the Arctic. @Curionic
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