It may be observed that nothing could be less artistic than a formal arrangement of such stones at regular intervals. Everyone, moreover, must have remarked the difficulty of keeping one's balance whilst stepping upon stones placed exactly in a row, a performance resembling that of walking upon a narrow plank. It is not, therefore, surprising to find that the Japanese gardener follows carefully devised rules for the distribution of "Stepping Stones." He uses certain special stones and combinations, having definite shapes and approximate dimensions assigned to them, and he connects these with secondary blocks, the whole being arranged with a studied irregularity for both comfort in walking and artistic effect. This is attained by the employment of ragged slabs of slate, schist, or flint, flat water-worn rocks or boulders, and hewn slabs or discs of granite or some other hard stone. The natural boulders are placed in zigzags of fours and threes, or sometimes in threes and twos, artificially hewn slabs, discs, or strips intervening. Though uniformity of tread is carefully calculated, the different sizes of the stones cause the intervals to vary considerably, and any apparent regularity is avoided. The distance between "Stepping Stones" should not, however, be less than four inches, to allow of the intermediate spaces being kept clean.