Two hundred years ago, a farmer in upstate New York discovered some giant bones while digging in peat bogs. Dubbed “The Great Unknown” by the newspapers, the findings attracted the interest of Charles Wilson Peale, creator of Philosophical Hall, the Philadelphia natural-history museum. Peale purchased the bones and then planned excavations in an effort to find a more complete skeleton. The search for the rest of the mastodon, the struggle to excavate, reconstruct, and display the skeleton are handsomely depicted in carefully researched paintings, often in sober earth tones. Scenes include not only the primitive means of retrieval and transport, but also snippets of daily life at the beginning of the 19th century. While the brown and bronze cover painting of a fossil skull hints of mystery, the author spoils the surprise of the mammoth discovery with a forward that shows it as it might have looked when it roamed the Hudson River region 12,000 years ago. Still, this inviting presentation has certain reader appeal and might even inspire future paleontologists. (further adult readings, glossary) (Nonfiction. 8-10)