At first glance, longitude doesn't seem like a topic with the makings of a page-turner. But under Louise Borden's sure hand, children and adults alike will find themselves caught up in the amazing saga of an important scientific challenge when they read Sea Clocks: The Story of Longitude.

For centuries, sailors were able to measure latitude, their location north or south of the equator, by using the sun and the stars. But determining longitude was a different matter. Over the years, many lives were lost at sea through miscalculations. Eventually, it was determined that the solution to the problem was a clock that could keep absolutely accurate time so that sailors could know what hour it was back at their home ports. In this way, they'd be able to calculate longitude. But building a sea clock proved to be difficult, since rolling ships and weather all affected the timepieces.

In 1714 the English Parliament offered a reward of 20,000 pounds sterling (equal to several million dollars today) to anyone who could build an accurate sea clock. The man who ultimately solved the puzzle was John Harrison, an English clock maker. The arduous task of building the device became his life's work. Although he had no scientific training, Harrison, along with his son William, struggled for more than 40 years to create a working sea clock, or chronometer, that met the requirements. Harrison actually built four different models and was finally awarded the prize in 1773, just three years before his death.

In her new picture book, Louise Borden manages a feat almost as difficult as Harrison's by making his story dramatic and accessible to young readers and explaining in simple terms the complexities he faced. Borden appropriately keeps the focus on the inventor's struggle, while offering a clear explanation of the significance of his work. Erik Blegvad's watercolors bring an elegant, old-fashioned feel to the narrative. With an author's note, as well as a short section on some facts of Harrison's life story, this is a wonderful work of scientific history that young readers will love.

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