[Sidenote: Propitiating tree-spirits in house-timber.] Even when a tree has been felled, sawn into planks, and used to build a house, it is possible that the woodland spirit may still be lurking in the timber, and accordingly some people seek to propitiate him before or after they occupy the new house. Hence, when a new dwelling is ready the Toradjas of Central Celebes kill a goat, a pig, or a buffalo, and smear all the woodwork with its blood. If the building is a _lobo_ or spirit-house, a fowl or a dog is killed on the ridge of the roof, and its blood allowed to flow down on both sides. The ruder Tonapoo in such a case sacrifice a human being on the roof. This sacrifice on the roof of a _lobo_ or temple serves the same purpose as the smearing of blood on the woodwork of an ordinary house. The intention is to propitiate the forest-spirits who may still be in the timber; they are thus put in good humour and will do the inmates of the house no harm. For a like reason people in Celebes and the Moluccas are much afraid of planting a post upside down at the building of a house; for the forest-spirit, who might still be in the timber, would very naturally resent the indignity and visit the inmates with sickness.[152] The Bahaus or Kayans of central Borneo are of opinion that tree-spirits stand very stiffly on the point of honour and visit men with their displeasure for any injury done to them. Hence after building a house, whereby they have been forced to illtreat many trees, these people observe a period of penance for a year, during which they must abstain from many things, such as the killing of bears, tiger-cats, and serpents. The period of taboo is brought to an end by a ceremony at which head-hunting, or the pretence of it, plays a part. The Ooloo-Ayar Dyaks on the Mandai river are still more punctilious in their observance of taboos after building a house. The length of the penance depends chiefly on the kind of timber used in the construction of the dwelling. If the timber was the valuable ironwood, the inmates of the house must deny themselves various dainties for three years. But the spirits of humbler trees are less exacting.[153] When the Kayans have felled an ironwood tree in order to cut it up into planks for a roof, they will offer a pig to the spirits of the tree, hoping thus to prevent the spirits from molesting the souls of persons assembled under the roof.[154]