His How did we find out ... series

Discusses the theories that led to the discovery that the earth was round.

Traces the history of man's study of fossils and explains what this study has enabled him to learn about the dinosaurs.

Traces the developing knowledge about germs from the first sighting of them under a primitive microscope to modern medicine's new methods of combating them.

Traces the origin of numbers and the development of the Roman, Egyptian, and Hindu systems of numerals.