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142 farmer and here found two kangs in separate sleeping apartments, both warmed by the waste heat from the kitchen whose chimney flue passed horizontally under the kangs before rising through the roof. These kangs were wide enough to spread the beds upon, about thirty inches high, and had been constructed from brick twelve inches square and four inches thick, made from the clay subsoil taken from the fields and worked into a plastic mass, mixed with chaff and short straw, dried in the sun and then laid in a mortar of the same material. These massive kangs are thus capable of absorbing large amounts of the waste heat from the kitchen during the day and of imparting congenial warmth to the couches by day and to the beds and sleeping apartments during the night. In some Manchurian inns large compound kangs are so arranged that the guests sleep heads together in double rows, separated only by low dividing rails, securing the greatest economy of fuel, providing the guests with places where they may sit upon the moderately warmed fireplace, and spread their beds when they retire.

The economy of the chimney beds does not end with the warmth conserved. The earth and straw brick, through the processes of fermentation and through shrinkage, become open and porous after three or four years of service, so that the draft is defective, giving annoyance from smoke, which requires their renewal. But the heat, the fermentation and the absorption of products of combustion have together transformed the comparatively infertile subsoil into what they regard as a valuable fertilizer and these discarded brick are used in the preparation of compost fertilizers for the fields. On account of this value of the discarded brick the large amount of labor involved in removing and rebuilding the kangs is not regarded altogether as labor lost.

Our own observations have shown that heating soils to dryness at a temperature of 110° C. greatly increases the freedom with which plant food may be recovered