<http://schema.org/caption>
"The Last Ride of the Pony Express - painted by  George M. Ottinger in 1873 - showing a Pony Express rider passing the work crews installing the Transcontinental Telegraph (Photo: The Athenaeum)"^^<http://www.w3.org/2001/XMLSchema#string>
<http://newatlas.com/last-telegraph-message/28314/>