The furnace has been described as situated in a pit. Situated on a bank or on sloping ground, it was easy to arrange for withdrawal of the furnace. In some cases this has not been possible, and various modifications have been effected. The most satisfactory yet encountered is that in which a shallow brick pit is surmounted by an iron cone, about 4 feet in height. This is fitted with a cap having small perforations. The fire burns in the pit, and the heat is radiated by the cone. It would have been more effective to have allowed greater height in the furnace chamber, and to have employed the travelling drum-furnace as in the original design. In order to avoid interference in draught by a space between the bottom of the doors of the compartments and the platform (due to the presence of rails), the floor of the platform is laid level with the top of the rails; or to the bottom of the doors is attached a swinging flap, notched for accommodating the rails when in position. * * * * * There are in use houses of other designs, which all more or less vary only in some modifications from the types described. Hence they do not call for special comment. Recently a rather distinct departure has been noted in a structure designated the "Barker" smoke-house. BARKER PATENT.--In essential this consists of a long narrow structure erected with an appreciable slope from one end to the other. At the lower end is a small furnace enclosed in a brick compartment. The smoke from this furnace travels up the slope to the other end, at which the rubber enters. The sheets are hung on bars which are attached to a unit framework. This frame slides, by its own weight, upon timber side supports. A sufficient number of these units occupies the full effective length of the structure. The removal of "stops" at the lower end enables the foremost frame to be removed, and the succeeding frames slide into a new position. Thus the freshly prepared sheets, entering at the higher end, gradually and automatically move towards the furnace as the frames of dry rubber are removed from the lower end. [Illustration: THE NEW "BARKER" TYPE OF SMOKE-HOUSE: A SMALL UNIT. The racks slide automatically from top to bottom on withdrawal of the lower frames through door at front. The furnace is contained in the brick compartment at the lower (front) end.] Thus far only small units have been seen. It is claimed that, properly prepared, sheet rubber can be smoke-cured in about five or six days, and it is stated that installations have been in successful working for sufficiently long periods to prove their efficacy. The device is better known in Java and Sumatra than in Malaya. The capacity of a unit building is stated to be 7,000 lbs. per month, calculating on a six days' cycle of working. In a more recent design provision is made at the lower end for a water tank, into which all rubber can be discharged in case of fire. CHAPTER XVI