shows four stones which are surrounded with the minimum number of stones. Plate 2, Diagram vi, shows the same group with a couple of helping stones added, which would probably be found necessary in actual play.
It follows from this rule that stones which are on the same line parallel with the edges of the board are connected, and support each other, Plate 2, Diagram vii, while stones which are on the same diagonal line are not connected, and do not support each other, Plate 2, Diagram viii. In order to surround stones which are on the same line, and therefore connected, it is necessary to surround them all in order to take them, while stones which are arranged on a diagonal line, and therefore unconnected, may be taken one at a time. On Plate 2, Diagram iii, if there were a stone placed at S 18, it would not be connected with the stone in the corner, and would not help it in any way. On the other hand, as has been said, it is not necessary to place a white stone on that point in order to complete the capture of the stone in the corner.
In order to capture a group or chain of stones containing vacant space, it must be completely surrounded inside and out; for instance, the black group shown on Plate 2, Diagram ix, while it has no hope of life if it is White’s play is nevertheless not completely surrounded. In order to surround it, it is necessary to play on the three vacant intersections at M 11, N 11, and O 11. The same group of stones is shown in Diagram x completely surrounded. (It may be said in passing that White must play at N 11 first or the black stones can defend themselves; we shall understand this better in a moment.)
In practice it often happens that a stone or group of