Kiln-dried lumber piled in storage rooms (without any heat) will absorb 7 to 9 per cent of moisture, and even when so stored should be tested for moisture before being manufactured into the finished product. Never work lumber through the factory that has more than 5 or 6 per cent of moisture or less than 3 per cent. Dry storage rooms should be provided with heating coils and properly ventilated. Oak or any other species of wood that shows 25 or 30 per cent of moisture when going into the dry kiln, will take longer to dry than it would if it contained 15 to 20 per cent, therefore the importance of testing before putting into the kiln as well as when taking it out. The Electric Heater In Figure 101 is shown the Electric Heater. This heater is especially designed to dry quickly the test pieces for use in connection with the Scalometer (see Fig. 100) without charring them. It may be attached to any electric light socket of 110 volts direct or alternating current. A metal rack is provided to hold the test pieces vertically on edge. [Illustration: Fig. 101. The Electric Heater.] Turn the test pieces over once or twice while drying. It will require from 20 minutes to one hour to remove all the moisture from the test pieces when placed on this heater, depending on whether they are cut from green, air-dried, or kiln-dried boards. Test pieces cut from softwoods will dry quicker than those cut from hardwoods. When the test pieces fail to show any further loss in weight, they are then free from all moisture content. BIBLIOGRAPHY AMERICAN BLOWER COMPANY, Detroit, Mich. IMRE, JAMES E., "The Kiln-drying of Gum," The United States Dept. of Agriculture, Division of Forestry. NATIONAL DRY KILN COMPANY, Indianapolis, Ind. PRICHARD, REUBEN P., "The Structure of the Common Woods," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 3. ROTH, FILIBERT, "Timber," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 10. STANDARD DRY KILN COMPANY, Indianapolis, Ind. STURTEVANT COMPANY, B. F., Boston, Mass. TIEMAN, H. D., "The Effects of Moisture upon the Strength and Stiffness of Wood," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 70. TIEMAN, H. D., "Principles of Kiln-drying Lumber," The United States Dept. of Agriculture, Division of Forestry. TIEMAN, H. D., "The Theory of Drying and its Application, etc.," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 509. THE UNITED STATES DEPT. OF AGRICULTURE, DIVISION OF FORESTRY, "Check List of the Forest Trees of the United States." THE UNITED STATES DEPT. OF AGRICULTURE, DIVISION OF FORESTRY, Bulletin No. 37. VON SCHRENK, HERMAN, "Seasoning of Timbers," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 41. WAGNER, J. B., "Cooperage," 1910. GLOSSARY