Photo provided by the United States Geological Survey/United States Department of the Interior
View this photo at pubs.usgs.gov
BH Photo #317197
Photographs #3 is described as the piers of the original bridge. In fact, this is the remains of a low water crossing that was, I believe, installed whilst the replacement bridge was under construction. The piers of the original bridge were constructed from large blocks of granite - many of which (perhaps all) are still lying around in the riverbed beneath the current bridge.
This is an interesting site. Thank you for making all this information available!