I alease liked optical illusions.I first discovered this effect seeing a pair of Brake pads for a garden tractor years ago.The customer & I noticed when the curved pads were sitting below,and above each other the upper pad looked shorter we thought they made them wrong,but when you placed them on each other they were the same size!!.This summer I learned its used as a magical effect.
Yesterday I used an old snow thrower auger to make several sets of these boomeranges.They are steel,and will hold up better than the paper set I have.

Enginemagic:

That's an interesting use for these! You've re-discovered the Jastrow illusion.

Among others, Leslie Melville has a great little story for this illusion in his book Magictales -- "The Strange Tale of Mr. Tall and Mr. Small"

I've also found myself stockpiling the convenience store coffee cup sleeves. Take a sharpie, draw a couple of eyes on them, and you're good to go with this illusion.

Another thread on this is here: http://www.themagiccafe.com/forums/viewt......orum=100

Thanks for the info.

That is good idea...:o)