Online I happened upon an image of a plain and relatively featureless manhole cover that reminded me of some of the scuff-worn manhole covers here in the city of Toronto. That lead to a quick search of manhole cover images and I was rewarded with a myriad of examples to feast my eyes upon. I can only say that I had no idea!

Simple, Utilitarian Manhole Cover in NOLA

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In a city where everything is extraordinary, this seemingly plain manhole cover located in New Orleans, Louisiana almost seems boring. It serves its purpose of course. Manhole covers might even be used for purposes not envisioned by their manufacturer. I have in~situ used manhole covers very similar to this in my costuming work that used pop rivets. I would use the flat-surfaced iron surface and a hammer to pound flat the rivet tails after joining together larger plastic carapaces. The surface of the manhole cover served as sort of an anvil. It was seeing this image that got me wondering what other types and designs of manhole covers might exist.

A Map of London Sewers, In Case You Get Lost

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Telephone Access Manhole Covers

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Not just for access to municipal sewer systems, manhole covers provide access to buried phone & communications lines, gas or steam lines, potable water supply, and other needs for urban life as we know it.

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A Warlord’s Shield?

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The author of this image cites that this particular manhole cover is of an older type belonging to the Tokyo Electric Power, Japan, dating to circa 1960’s. When I saw this one I could not help but see a warrior’s shield.

Firefighter Manhole Cover

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 -Have you ever noticed that what is mundane in any other country is always something extraordinary in Japan? Manhole covers are no exception!

Bejeweled Manhole Cover in Rhode Island?

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Are they amethyst? Is it colored glass? These are actually glass prisms that refract light into the dark space below created possibly in the day before electric illumination. Its purpose is clearly to guide repairmen working below to where the exists are should they become separated or lose their way in the dark if their lantern extinquished.

This link below may very well be the source of the passive sunroof manhole covers shown above, a glimpse into the previous century and how things were done before electric modernization.

See: Jacob Mark & Sons Vault Lighting

How Wooden Sailing Vessels Were Illuminated Below Deck

Old wooden sailing vessels used something similar; a non-flame way to illuminate below deck which worked of course, only during the daylight hours. It was solid glass pyramid-shaped object (see diagram below) about the size of a small cantaloupe. These employed a large square base attached to the bottom of the pyramid by a small square pedestal neck. It was one solid piece of glass, cut and polished to transmit and disperse daylight.

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Installed pointy-end downwards into the wooden deck, the square base was seated level into the deck and sunlight would filter through the hand-blown glass providing some passive light during the day to the deck below. The four sides of the pyramid would disperse the light to all corners of the room. The points of contact with the deck were water-tight of course.

These early glass skylights are sometimes found washed upon ocean-facing beaches or found on the sea floor near known wrecks of galleon sailing ships of previous centuries. Their design is similar to the camera obscura devices which projected enlarged images onto walls through lensing principles and prism action.

A valuable collector’s item these ceiling lights of the days of sailing vessels, often people whom have or acquire these in curio shops don’t even know what they have.

Alligators in the Sewers?

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As if there were not enough deterrent to stay topside, a reminder that that may be Cayman below would keep even the Phantom out of the sewer network. I am reminder about square manhole covers. I think that Microsoft University uses square manhole covers statedly ‘to be different.’ Just like their software, -could a square manhole cover could be considered to be broken by design? A round manhole cover will not drop into he hole it covers while a square manhole cover will fit diagonally through the hole and drop inside. -A chance for vandalism. While a round hole might make it slightly more difficult to get in and out of for sewer/telephone workers, it is for their benefit. Have you ever noticed that manholes in the ground are a relatively tight fit? The ’smaller hole’ is actually designed this way as a safety feature. A worker might slip entering or leaving a manhole but by virtue of the smaller entry will get caught by his elbows, clothes or armpits perhaps thus averting a more serious injury from an uninterrupted fall.

Advantage: round manhole cover. A circle is the strongest shape afforded and can withstand more compression of the earth around them. And circular manhole covers are easier to make. A round iron object can be milled on a lathe easiest to ensure uniformity. A square or rectangle manhole cover requires more work and is prone to warping from traffic passing over them.

When a ’street racing’ event is sanctioned and permitted, manhole covers must be welded down. The combined effects of speed and aerodynamic lift of the car passing rapidly over a manhole can actually lift a manhole cover up from its grate, possibly with disastrous results to the car behind.

Wikipedia cites that in Montreal in the year 1990, World Sportscar Championship racer Jésus Pareja’s struck a manhole cover that was sucked up by the vacuum effect of the racer in front of him, causing his car to catch fire.

Manhole Cover in Outer Space?

A urban myth (which may be factual but the main evidence is missing) states that a manhole cover may have been blasted into outer space in the 1950s in a test of an atomic explosion. Operation Plumbbob had a 900kg steel plate that was blasted off the end of a test shaft at an estimated speed of six times Earth’s escape velocity.

The math calculation is cited to possibly be incorrect (probably less than 6X escape velocitu but still..) the manhole cover was never found and thus, the myth endures. The speed of ’six times escape velocity’ may be in part based upon photographic evidence only: a single photographic frame that shows a solid vertical blur that is identified as the manhole cover. The speed of the exposure and the height of the blur could be explained mathematically and might be the main source of this velocity data. I would love to find out someday that NASA finds a radioactive manhole cover orbiting the sun somewhere out there in interplanetary orbit. That would be totally awesome and inspiring. Think about this for a moment; the Soviet Union’s (and the world’s, for that matter) first man made satellite was Sputnik 1, launched on October 4th, 1957. If we discover that an American made & launched manhole cover is in space then it is was the U.S. that sent the first man made object into outer space, not the U.S.S.R.

It is generally believed however that the manhole cover was vaporized by the atmosphere due to the high velocity. -A meteorite, in reverse.

If this manhole cover is someday in the future found orbiting the sun it would not reduce the triumph of achievement that was Sputnik 1, but it would rewrite the history books with an existential twist of strange fate with a humorous side note.