Oakland Underfoot

When I featured the Ransome Company here a few weeks ago, that post showed the firm’s various sidewalk stamps. But they also made steel things — at least, they made access covers. This one, on La Salle Avenue in Piedmont, is really pleasant to look at.

Which point is the top?

Access covers are typically busy with “treads” and symmetrical in pattern. The treads are mandatory (for traction, cleanliness and protection against wear), but symmetry is just an aesthetic preference. Back in geology school when I took my mandatory semester of crystallography, we were trained to look at patterns of dots, say, and detect all the ways they were symmetrical. Some arrangements of atoms in a crystal, or the faces of a crystal, look the same after you rotate them by 180 degrees, others after rotations of 120 degrees — or 90 or 60 degrees. Or if you imagine placing a mirror, on edge, across the center of the pattern, the reflection may exactly duplicate the side behind the mirror — that would be mirror symmetry. Every crystal on Earth exhibits one or more of these basic symmetries.

So I often find myself looking at the symmetry of an access cover to determine up and down. Looking only at the sets of holes, seven and five, at the center, you can picture two different lines running through the center that would split them into mirror-image halves. One line would run through the two blue paint spots; the other, at right angles to it, would run from the R in Ransome to the second T in Contractors.

Of course, the words around the rim are symmetrical across the first line, so that rules out the second. That would put the top of the lid between “Oakland” and “Cal.” Ransome was real particular about those five and seven holes.

But then there are the stars. They would be symmetrical across the first line too, except that a single star is missing. The designer of the mold either overlooked that, or decided to mess with our heads. (I think someone at Pheonix Iron Works played the same trick.)

Now PG&E and Great Western Power Company were both very meticulous about their symmetry, but Ransome’s access covers were just a little funky.

This entry was posted on 6 October 2017 at 8:02 am and is filed under  Access covers. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.