How about a water pistol?Obviously you'd have to be there to operate it, but if you're not you wouldn't see a cat anyway. You would also have the satisfaction, if you were accurate, of sending a damp moggie home to its owner!I suppose if you put fluoroscein in the water the cat would glow in the darkness so you could re-soak it! Somebody, a UK university professor I believe, came up with the idea of light-emitting particles in dog food. This was in order to avoid that dreaded "silent" footstep on the footpath...
Alan Brainsby ● 6392d