Among the Japanese the kilns are arranged in a peculiar manner. That in which the first firing is done is a small furnace, used only previous to the painting. The oxide of cobalt, which is more extensively employed than any other, is laid upon the white clay coating, and the piece is then glazed, usually in a compound of felspath and wood-ashes. The second firing then takes place. The kilns are built in terraced rows of from four to twenty, and rise about three feet above each other, growing larger in size as they extend up the hill. The ground-plan is trapezoidal, and the walls rise vertically for a few feet, and are then rounded off into an arch. The front wall, looking toward the lower end of the row, is pierced with holes near the ground, and others are made in the back wall at about three feet above the ground, so as to open directly upon the floor of the next kiln above. The draught in this way rushes through the entire row toward the chimneys behind the largest and uppermost kiln. The fuel is thrown directly into the kiln, and not into a fireplace. It is arranged along the lower side in a narrow space divided from the rest of the kiln by fire-clay slabs set upright. The fire begins in a furnace attached to the lowest kiln. The hot air rushes through the air-holes into the next kiln, which is thus heated before its own firing begins, and so on throughout the entire range, the kilns furthest up the line having thus to stand the highest temperature. Each one has the benefit of the heat of all the lower ones. The Japanese do not make any extensive use of seggars. To keep the pieces free from dust or falling particles of the vault, the inside of each kiln is glazed before the firing begins. The pieces are placed one above another upon fire-clay stands. The small kilns for the preliminary firing are in the potter’s yard, but the kilns above described belong to the community, and are rented to the manufacturers. [Illustration: Fig. 27.--Hard Pottery Kiln.] [Illustration: Fig. 28.--Porcelain Kiln.]