"The cubic capacity is 2,048 cubic feet. As there are no gangways, etc., this is fully utilised. This gives a rate of monthly output capacity to over 10-1/4 lbs. dry rubber per cubic foot of drying space; an excellent figure much in advance of values obtained in the great majority of ordinary smoke-houses."[18]
[18] Since the above was written, it has been found possible to eliminate the gauze. A mild steel top has been made, perforated with 2-inch holes. Practically no dust is ejected from the furnace, and there are no flames.
Owing to shortage of supplies during the War, similar buildings have been erected with frames of well-seasoned hard wood, which was protected by strips of asbestos-slate or galvanised iron. The latter material was also substituted in the covering walls. Later, houses were erected of brick, with other minor modifications. As a natural development, the latest buildings consist of two of the original houses face to face, under a common roof, and served by common platforms.
As originally designed, the house was intended to meet the needs of a small estate, or a division of an estate, having a maximum output of about 20,000 lbs. of sheet rubber per month. The possibility of an extension of this idea has been shown to be great.
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.