Slate’s Jacob Brogan looks at the Osher Map Library and its decade-long project to digitize its collection of maps, atlases and globes, and ruminates on the advantages and disadvantages of digitization.

Digitization also presents scholars with a new way of looking at maps, since, according to Fowler, “you can get a lot more detail than you could even looking through a magnifying glass.” As Matthew Edney, Osher professor in the history of cartography, pointed out, you can also dwell on an image longer than you could while studying a physical item under controlled conditions. “Rare book rooms kick you out,” he told me, but you can take your time with digital copies.

In some cases, that’s allowed Edney to discover new features of maps that he thought he already knew well. He points in particular to an 18th-century map of New England that was once owned by Hugh Percy, a British army officer who was a key player during the battles of Lexington and Concord. “Staring at it on screen, you realize there are these faint pencil lines, possibly indicating tentative knowledge,” Edney said. As he explains in a recent paper on the topic, such observations helped him better understand how Percy likely used the map—offering a picture of what the map meant at the time and not just what it shows.

Previously: A Look at the Osher Map Library.