Tim Marx was 9 years of age. P was 8, and Barbara Corcoran was also 8. They are the only eyewitnesses to the episode under examination. Tim and P were on the front lawn of the Singer residence. Barbara was riding a bicycle back and forth on the pavement. Tim had been throwing rocks into or across the street and talking about how far he could throw. Neither girl threw any rocks or clods. Immediately preceding Tim's striking P in the eye with a rock, which he admitted, Barbara was riding easterly on the sidewalk and entering upon the Singer property at the west side, about 30 feet from P. Tim, who was looking at P, said to her, 'watch Barbie.' He had not previously thrown at her or Barbara. P looked toward Barbara and then back at Tim and at the same moment was struck in the eye by the rock, which was a flat, rough one about the size of a small hen's egg. Barbara saw him throw at an angle toward her; saw him let go of the rock but did not see it strike P. For the rock to strike P, one of two things would have to occur, either (1) Tim changed the direction of throw without any warning, or (2) he held the rock too loosely, or let go of it too soon to control its flight and inadvertently hit P. The evidence is susceptible of either of these inferences. P sued D for battery and his parents on the theory of their negligent failure to control D's known penchant for throwing rocks at other people. P's father also sued the parents of D for recovery of expenses incurred by him as a result of his child's injury, the charge being negligence upon the part of the parents. The trial judge granted a nonsuit as to both Ps and all causes of action. Ps appealed.