Houston Belt and Terminal Railway Bridge over Buffalo Bayou, Houston, Texas. The semi-circular rack was turned by the pinion, raising the bridge.  The rotation of the raising or lowering bridge was about the trunnions. (See: <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/nakrnsm/5004601153/">www.flickr.com/photos/nakrnsm/5004601153/</a>)
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/32345848@N07">Patrick Feller</a> from Humble, Texas, USA
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/nakrnsm/5004756867/">Rack, HB&amp;T Railway Bridge over Buffalo Bayou, Houston, Texas 0911101457BW</a>