Slow in school but gifted as a craftsman, in 1851 Foucault was the first to find a way to demonstrate the earth’s spin on its axis, using a pendulum. Mortensen invites young readers into this French scientist’s life with a quick description of his childhood difficulties, but the focus of this enjoyable story is the “beautiful experiment” for which he’s noted. The author describes earlier efforts to show the earth’s spin and goes into detail about the accident that gave Léon his insight, ending her account with his demonstration before a distinguished crowd. Allén's digitally finished pencil-and-watercolor paintings in browns and deep reds vary in size and placement on the page. They add to the sense of time and place but are less successful in illustrating the actual experiment. A series of small paintings shows the rod wiggling in the lathe, but in a similar series the pendulum’s movement away from the longitude line is less clear. Readers will come away with a better sense of the history than the science. (author’s note, illustrated glossary, bibliography) (Informational picture book. 7-9)
