Marvin the Mower

On the roof of the Underground Gallery at the Yorkshire Sculpture Park there is a solar powered robot mower. It performs a circle, thinks a bit, then a straight line, thinks a bit more, then a long curve. It is engrossing, especially the thinking bits. I have just learned that two previous mowers had flung themselves off the grass roof. Concerned, I am attempting to detect signs of acute depression. Thus far, I can only see mild, wistful sadness combined with a hesitant commitment to obligation. But you never know.