Four balls, sometimes six, are said to constitute an "over," and at the completion of each over the bowler is relieved by an alternate, who bowls from the opposite wicket, the fielders meantime crossing over or changing places, so as to preserve their relative positions toward the active batsman for the time being. Any over during which no runs are earned from the bat is said to be a "maiden" over, and is scored to the credit of the bowler as an evidence of good bowling. In addition to the runs earned on hits there are certain "extras," which, though scored as runs in favor of the _in_ side, are not strictly runs, but are imposed rather as penalties for bad play by the outs than as the result of good play by the ins. Thus, should the bowler bowl a ball which, in the opinion of the umpire, is outside the batsman's reach, it is called a "wide," and counts one (without running) to the batsman's side; should the bowler in delivering a ball step beyond the bowling-crease, or if he jerks it or throws it, it is a "no ball," and counts one (without running) to the batsman's side; but if the batsman hits a no ball he cannot be put out otherwise than by being "run out." If he makes one or more runs on such a hit, the no ball is condoned, and the runs so made are credited as hits to him and his side. The umpire must take especial care to call "no ball" instantly upon delivery--"wide ball" as soon as it shall have passed the batsman, and not, as a confused umpire once called, "No ball--wide--out." Again, should a ball which the batsman has not touched pass the fielders behind the wicket, the batsmen may make a run or runs, which count to their side as "byes:" should the ball, however, missing his bat, glance from the batsman's leg or other part of his body, and then pass the fielders, the batsmen may make a run or runs, which count to their side as "leg-byes." The game thus proceeds until each batsman of the _in_ side is in turn put out, except the eleventh or last, who, having no partner to assume the other wicket, "carries out his bat," and the innings for the side is closed. The other side now has its innings, and, _mutatis mutandis_, the game proceeds as before. Usually two innings on each side are played, unless one side makes more runs in one innings than the other makes in both, or unless it is agreed in advance to play a "one-innings match."