Convert from marathon to chain [Ramsden, engineer]

Unit Definition (marathon)
A long distance event based on an ancient Greek event, run over a distance of just over 26 miles.

Unit Definition (chain [Ramsden, engineer])
The Ramsden chain is quite different to the Gunter chain. The Ramsden chain was commonly used by American surveyors. It equals approximately 100 feet and is also known as the engineer's chain.