by the circulation of warm but very moist air. Its operation is automatic, no machinery or power being required. The apparatus consists of specially arranged steam radiator coils, in which exhaust or live steam may be used; they are placed beneath the rails near the discharging end of the building. Air flows under the radiator coils, and rises, at the same time travelling through the stacks of wood, thus gradually drawing moisture from it. As the air becomes more laden with moisture it sinks between the rails and flows towards the loading end, where it is allowed to escape. This circulation may be regulated by a few simple dampers. The timber is dried from the centre outwards, the surfaces finishing last; therefore case-hardening, splitting, warping and other injuries are prevented. By this system it is claimed that timber which would require a year to dry in the open can be dried in a week; this, of course, is a great advantage.
Artificially Seasoning Timber Small Stuff.
A method sometimes adopted for seasoning small pieces of timber, especially for tool making, and other purposes, is possible wherever a supply of steam—from the boiler or exhaust of a steam engine—is available. The pieces of wood are stacked in a steam chest (see Fig. 131) or a barrel (Fig. 132) and allowed to become thoroughly
Fig. 131.—Steam Chest for Small Pieces of Timber.
saturated with steam; This will take from two to twelve hours, according to the kind and thickness of the wood. No pressure is required, but the door of the chest or top of the barrel should be closed with a lid; the fitting is not close, allowing the steam which has circulated round the wood to escape. For this reason the apparatus is kept outside a building. The material being treated is kept from the bottom proper to allow the steam to become evenly distributed. The use of this method is very limited, because by it the natural colours
