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>>PS is that how you guys spell "plough"?
>
>I had typed "plough" but then realized that here the word "plow" is used, so I changed it.

Strange. YOU know the classic spelling but other canucks don't, and use "plow" instead. You're the second to mention ploughing reP: cats' eyes and both of you used "plow". How do you spell "draught" as in "draft beer"? - "Draft"?

>
>Obviously, if a cat's eye has to be sunken into the road surface then it cannot be fired from a gun.

Why not? It's like a mechanical lance that embeds the eyes into the (yielding) tarmac. Mind you, if you've ever looked closely at eyes then you'd see they're a piece of work, probably quite expensive.