Spring diagram: Image courtesy of the Posner Memorial Collection, Carnegie Mellon University Libraries; London’s Memorial Tower: Matt Bridger / ​ DHD Multimedia Gallery; Royal Observatory: © National Maritime Museum, London
Atsperes shēma: Image courtesy of the Posner Memorial Collection, Carnegie Mellon University Libraries; Londonas Monuments: Matt Bridger / DHD Multimedia Gallery; Karaliskā Griničas observatorija: © National Maritime Museum, London