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:
The Quarterly journal of the Geological Society of London . PROCEEDINGS OF THE GEOLOGICAL SOCIETY April wave returning into the mass in the reverse direction but with that we are not here very much concerned This is rendered evident to the senses by the analogous movements of line of billiard balls fig When line of such