Page:Floor games (IA floorgames00well).pdf/116

make them have level-crossings, at which collisions are always being just averted; the lines go over and under each other, and in and out of tunnels. . . .

The marble tower, again, is a great building, on which we devise devious slanting ways down which marbles run. I do not know why it is amusing to make a marble run down a long intricate path, and dollop down steps, and come almost but not quite to a stop, and rush out of dark places and across little bridges of card: it is, and we often do it.