This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Summation Chain. en The summation chain runs around pulleys on Tide Predicting Machine No special purpose mechanical analog computer for predicting the height and time of high and low tides The pulleys move up and down and the chain sums their displacements to compute the height or time of high and low tides The government used