v.1. The Smithsonian Institution.
v.2. The sun and the welfare of man.
v.3. Minerals from earth and sky (Part 1. The story of meteorites; Part 2. Gem and gem minerals).
v.4. The North American Indians.
v.5. Insects, their ways and means of living.
v.6. Wild animals in and out of the zoo.
v.7. Man from the farthest past.
v.8. Cold-blooded vertebrates (Part 1. Fishes; Parts 2 and 3. Amphibians and reptiles).
v.9. Warm-blooded vertebrates (Part 1. Birds; Part 2. Mammals).
v.10. Shelled invertebrates of the past and present.
v.11. Old and new plant lore.
