The Polar World / A popular description of man and nature in the Arctic and Antarctic regions of the globe — G. Hartwig
The Sea and Its Living Wonders / A Popular Account of the Marvels of the Deep and of the Progress of Martime Discovery from the Earliest Ages to the Present Time — G. Hartwig
The Subterranean World — G. Hartwig
The Tropical World / Aspects of man and nature in the equatorial regions of the globe. — G. Hartwig
