A surprise on Lancaster Street

I spotted this small, but very distinctive manhole-like cover on Lancaster Street between Lark Street and Washington Park just this weekend.

It was those round cabochons of purple glass that caught my eye. Rather fancy for an apparently utilitarian metal lid in a sidewalk, though it matches rather nicely with the matched row of brownstones lining Lancaster Street. Of course, some of the glasses are missing...in one place, there's just a dark hole. A few yards away, there is another cover with a similar metal design that did not include the glass.

The edge of the cover reads Jacob Mark Worth Street NY. And there is a patent date...1873.

http://glassian.org/Prism/JacobMark/index.html

A quick bit of research over my morning coffee turned up a little information on this company. These are called "illuminated covers" or "vault lights" and they were intended to bring light into basements and other below-ground chambers with little or no other light sources. The rounds of purple glass are actually prisms which direct the light into the undergrounds spaces.

Vault lights were first patented in 1845 and were later used to bring light to early subway platforms. They are much more common - and there are much larger specimens from a variety of makers - scattered around lower Manhattan. There are examples of Jacob Mark vault lights on Hudson Street and Duane Street in Manhattan. Knowing me, I'll probably go out of my way to find them on my next trip down to the City.

But, for now, I'm rather curious why a small vault light was installed on a quiet street in Albany...and just what was originally illuminated by those amethyst-colored prisms.