Convergence is a compact manual rolling ball sculpture measuring 21 inches high by 17 inches wide and 17 inches deep. It is built entirely from stainless steel and uses colorful glass marbles. Unlike my motorized sculptures, this one does not use a lift or require any power. The marbles are picked up by hand at the bottom and placed into a queue at the top of the sculpture.

A release lever at the top lets you send one, two or all of the marbles onto the tracks at the same time. There are two separate tracks. The first is a shorter loop-de-loop track. The second is a much longer path that wraps around the frame and includes a section of wavy track, a reverse ball drop, a tipping arm that can handle and separate multiple marbles, and a lower section that runs through a spiral.

Both tracks eventually arrive at the same point at the bottom, but they approach it from opposite directions. That opposing motion is what gave the sculpture its name - Convergence.

Because this is a completely manual desktop sculpture, there is no motor, wiring or electrical outlet required. It is extremely portable and can be moved from a desk to a table or taken to another location without having to set anything up. The manual design also eliminates the powered lift and moving drive components found on motorized sculptures, making it especially simple for children to operate and experiement with.