Gravity is a mystery,
1915- Branley, Franklyn Mansfield
Paperback
(New York, Crowell [],, Aug. 16, 1970)
"A 'Let's Read and Find Out Science Book' that is planned for the child who is eager to know. It presents basic science information; are written with an understanding of how children think; are brief enough for the young child to cope with; are long enough to challenge them."