This method of kiln-drying depends on the maintenance of a high velocity of slightly superheated steam through the lumber. In few words, the object is to maintain the temperature of the vapor as it leaves the lumber at slightly above 212 degrees Fahrenheit. In order to accomplish this result, it is necessary to maintain the high velocity of circulation. As the wood dries, the superheat may be increased until a temperature of 225 degrees or 230 degrees Fahrenheit of the exit air is recorded. The 1-inch green gum was dried from 20.1 per cent to 11.4 per cent moisture, based on the dry wood weight in 45 hours. The loss due to checking was 10 per cent. Nearly every knot in the heartwood was checked, showing that as the knots could be eliminated in any case, this loss might not be so great. It was significant that practically all of the checking occurred in the heartwood. The loss due to warping was 22 per cent. Of course this was large; but not nearly enough crossers were used for the gum. It is our opinion that this loss due to warping can be very much reduced by using at least eight crossers and providing for taking up of the shrinkage. A feature of this process which is very important is that the method absolutely prevents all sap staining. Another delightful surprise was the manner in which the superheated steam method of drying changed the color of the sapwood from pure white to a beautifully uniform, clean-looking, cherry red color which very closely resembles that of the heartwood. This method is not new by any means, as several patents have been granted on the steaming of gum to render the sapwood more nearly the color of the heartwoods. The method of application in kiln-drying green gum we believe to be new, however. Other methods for kiln-drying this green stock are to be tested until the proper process is developed. We expect to have something interesting to report in the near future.[1] [Footnote 1: The above test was made at the United States Forestry Service Laboratory, Madison, Wis.] SECTION XII TYPES OF DRY KILNS DIFFERENT TYPES OF DRY KILNS Dry kilns as in use to-day are divided into two classes: The "pipe" or "moist-air" kiln, in which natural draft is relied upon for circulation and, the "blower" or "hot blast" kiln, in which the circulation is produced by fans or blowers. Both classes have their adherents and either one will produce satisfactory results if properly operated. The "Blower" or "Hot Blast" Kiln The blower kiln in its various types has been in use so long that it is hardly necessary to give to it a lengthy introduction. These kilns at their inauguration were a wonderful improvement over the old style "bake-oven" or "sweat box" kiln then employed, both on account of the improved quality of the material and the rapidity at which it was dried.