In the two photographs of old Forbes Field, there is a strange strip of material running in foul territory parallel to the third base line. In the second linked photo, it connects with a larger patch of the same material right behind home plate. Does anybody remember what these were for?
Is this the auto-tarp? Fred Clarke patented a device to cover the infield quickly, and I think that’s it.
From here:
I’ve crossed Forbes Field’s home plate myself at least 100 times, but never touched it. 
Sorry for the tri-post, but here’s the patent itself. Note the larger rectangle for the gear box/crank. It’s on the home plate side, and that’s the larger area you see near the umpire in your original pictures.
Thank you! I haven’t been wondering my whole life or anything, but I saw a picture a month or two ago and had no idea what it could be.
It sounds really cool, but I can’t seem to Google up any photos of it in action (film would be really nice).
Dennis