Evening Light on Temple Crag

This shot was captured at the end of my second day on the trail. Yes, I take my time getting to the sweet spots. A small footbridge with rails provided a crossing over the outlet from Second Lake to the eastern side. I have to wonder at the obvious efforts put into controling the flow of water from this lake into First Lake. There is a sluice gate, a rampart and wooden supports, and this little footbridge. Does anyone know the history of these man-made artifacts?