One thing I would have liked the article to explain is when this is preferable over solid glass.
Presumable cost or manufacturability? Big sheets of glass were not feesible in the 1800s
What are those grids of glass in the sidewalk and why are they purple?
21–30 of 120 posts
Re: What are those grids of glass in the sidewalk and why are they purple?
#22One thing I would have liked the article to explain is when this is preferable over solid glass.
Tempered glass is relatively modern. They didn't have strong solid single panes of glass back then; the concrete with glass inlays was the best way to make it stand up to traffic above.
Re: What are those grids of glass in the sidewalk and why are they purple?
#23This is interesting, but raises a question. The article mentions: In San Francisco, vault lights are mostly used to illuminate sub-sidewalk basements — ie. basements that extend under the sidewalk. How does this work, legally? Where I live, sidewalks are property of the city (or the HOA, in some cases), and I'd presume the same in SF. Does the title of the sidewalk-adjacent property allow you to excavate N feet beyon…
It depends on how the lines are drawn. If you want to plow a road through existing houses today, it gets condemned -- taken by the government, lock, stock and barrel. In a new subdivision, they'll often deed the streets over to the city.
But sometimes, especially in the old days, the city just got a "right of way," not title to the land. And in that case, the owner could do anything it wanted, so long as it preserves the right of way. So if the city had a right of way to a sidewalk, it doesn't matter what you do under the sidewalk. Here's an interesting discussion about right of way edges that appears to use Washington (State) law.[0]
[0] http://mrsc.org/Home/Stay-Informed/MRSC-Insight/November-201...
Re: What are those grids of glass in the sidewalk and why are they purple?
#24One thing I would have liked the article to explain is when this is preferable over solid glass.
Safety/stability, presumably, given that people might stand on top of them (many of the examples here are embedded in sidewalks) and they'd need to be weight bearing. Safety glass is a relatively more recent invention than some of the examples (at least one example in the article dates back to the mid 19th century), and a very recent invention if specifically restricting to the types of plastic-based laminated glass trusted in things like modern car windshields and observation floors today.
Re: What are those grids of glass in the sidewalk and why are they purple?
#25One thing I would have liked the article to explain is when this is preferable over solid glass.
Safety/stability, presumably, given that people might stand on top of them (many of the examples here are embedded in sidewalks) and they'd need to be weight bearing. Safety glass is a relatively more recent invention than some of the examples (at least one example in the article dates back to the mid 19th century), and a very recent invention if specifically restricting to the types of plastic-based laminated glass…
Also, the article points out that many of them had interesting prismatic shapes to bounce light around in interesting directions, and making those prisms would be easier as smaller individual components rather than one large piece of glassblowing, even if they had the technology to make it safe enough at that size.
Re: What are those grids of glass in the sidewalk and why are they purple?
#26This is interesting, but raises a question. The article mentions: In San Francisco, vault lights are mostly used to illuminate sub-sidewalk basements — ie. basements that extend under the sidewalk. How does this work, legally? Where I live, sidewalks are property of the city (or the HOA, in some cases), and I'd presume the same in SF. Does the title of the sidewalk-adjacent property allow you to excavate N feet beyon…
That must be a western concept. On the east coast it's common for sidewalks to be owned by the landowner yet have to remain unencumbered for the public right of way. Some owners find out the hard way that they are also responsible for maintaining the sidewalk when the city hits them with a notice.
Re: What are those grids of glass in the sidewalk and why are they purple?
#27Denver has these, you can see them on Larimer and Market street in LoDo. Around the 1890s, the locals dug out a series of tunnels through the city. The snows would come in and people would just go underground for a few days for business. There was a bar that closed about a year ago called the Blake Street Vault—it used to be a bank—and if you asked they would take you into the basement to see the vault and the dumbwaiter. You can see down where they plastered over some of the wall, it used to have a teller window right there open to the tunnels for customers.
Supposedly, you could go from Union Station all the way to the capital building underground (but I doubt that).
I’m sure most of the tunnels aren’t passable, possibly collapsed, filled in, or flooded. But I seriously want to go down and try to map out some of them to be restored like they did in Seattle.
Re: What are those grids of glass in the sidewalk and why are they purple?
#28Modern people accustomed to ubiquitous electrical lighting would probably think of 19th century and beyond as quite dark.
Re: What are those grids of glass in the sidewalk and why are they purple?
#29Thaddeus Hyatt, the inventor of those grids, has a fascinating history, including backing militant abolitionists (I think it's unknown whether he bankrolled John Brown) and being jailed by the Senate (?) for refusing to testify.
Wikipedia states his financial support of John Brown as fact: https://en.wikipedia.org/wiki/Thaddeus_Hyatt
Re: What are those grids of glass in the sidewalk and why are they purple?
#30I had a sail boat where the prior owner had installed 4 of these in the cabin roof. They were little domes and did a good job of lighting the cabin in the day, and marking a path at night.
Yes had one in my old boat. Nice, but not so nice where I'd install them on my current sailboat.