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Next put on tow long logs, roll them onto the middle, taking care to change off, so the big end at a given corner may be followed next time by the small end and insure the corner rising evenly. Roll one of these large logs close to where it is to be


placed, then cut on its upper surface at each end a notch corre-sponding with the ridge on the log it is to ride on. When ready, half a roll drops it into place. The log should be one to three inches above the one under it, and should not touch except at