Common name for chatoyancy, the appearance of a gemstone with impurities (inclusions) of a different color than the stone lined up down the middle of the crystal like a cat's long pupil.

Some people say that the only stone that can be called just "cat's eye" is the cat's eye chrysoberyl and every other mineral that exhibits chatoyancy is named "cat's eye (name of mineral)."

A term commonly used in games (such as Tic Tac Toe) in the instance that a "tie" is called; when the game can progress no further and there is no clear winner.

Cat's eyes are small devices designed to mimic the reflective properties of cat's eyes. In Britain they are set into some roads so that drivers can use the spots of reflected light to find their way along roads in the dark.

Cat's eyes were invented by a Yorkshire roadworker called Percy Shaw.

The story goes that one day Percy was driving home in the dark down a deserted road when he saw two spots of light in midair in front of him. These small circles of light were in fact his car headlights reflecting off the eyes of a cat which was sitting on the fence by the side of the road. If the cat hadn't been there Percy would not have realised that the road turned a corner at that point and would doubtless have driven straight on through the fence and to his death at the bottom of the steep hill beyond it.

This near death experience shook him up so much that he spent the next year trying to invent something like the eyes of a cat which could guide drivers in the dark.The resulting "cat's eyes" consisted of two prisms and an Aluminium mirror behind them to reflect some of the light form car headlights back into the eyes of the driver.

Unfortunatly his inventions soon became dirty in the middle of roads so he modified the design so that when cars drove over the rubber casing of a cat's eye the prisms inside were pushed past a rubber pad which wiped them clean.

On April the 3rd 1934 Percy laid his first fifty cat's eyes on a stretch of road near Bradford which was renouned for accidents. The number of crashes dropped dramatically and the ministry of transport approved Shaw's idea and began to install cat's eyes across the country.

Percy Shaw's invention made him a millionaire and in 1965 the Queen awarded him the OBE.

Today cat's eyes are used all over England and have probably saved thousands of lives. They are now also colour coded as follows.

WHITE        Separates lanes of traffic going in opposite directions.
AMBER        Marks the offside of motorways.
RED          Marks the nearside of motorways.
GREEN        Marks public sliproads.
BLUE         Marks police only sliproads.

Cats' eyes is the name of the small reflective devices placed on the road so drivers can see lane divisions in the dark. (At least, that's what they're called in Ireland). They get the name from the way in which they appear to glow unnaturally in the dark, like cats' eyes.

Normally, white cats' eyes are put in the middle of the road, dividing the traffic going in different directions (where the white dashed line is), and orange cats' eyes are put between lanes going the same direction and between the outermost lane and the side of the road (where the orange lines are). (I believe the colours are reversed in the U.S.A..) In addition, about 10 to 20 cats' eyes on the outside of the road are green where another road intersects (which is too small to be worth putting in a traffic light (stop light)), this allows the driver to know when to use the indicator (turn signal), allows enough time to slow down, and easily identifies exactly where the intersection is (the cats' eyes return to orange immediately after, so it's always between the last green cat's eye and the next orange one).

This means there are 3 types of cats' eyes: white on both sides, orange on both sides, and orange on one side but green on the other. The orange/green ones must be oriented correctly so oncoming traffic always sees the green side before and the orange side after, no matter which direction the traffic is coming from. (Rarely are two intersections so close together that green/green cats' eyes are necessary.)

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