Among the ancient Norse legends one tells of the visit of Thor, the mighty thunder god, to the land of the giants where he found them playing games of skill and strength. Eagerly he accepted their invitation to try his own prowess. His first test was to empty a great two-handed drinking bowl filled with a strange green liquid. But hard as he tried he succeeded in making it recede only a little bit. He shook his head perplexed as he put down the great bowl. Perhaps we should give you something easier, said the giants, and told him to lift a black cat walking about. This will be easy, said Thor to himself, as he seized the animal. But try as he might, strain and tug, he was unable to lift the animal. Now, now, sympathized the giants, we thought you were strong. Why don’t you wrestle with thi…