=Bulletin No. 11=--The Theory of Linear-Sinoidal Oscillations. By Henry Godfrey Cordes. 1920. 24 pp. Price, 40 cents. =Bulletin No. 12=--Motor Truck Logging Methods. By Frederick Malcolm Knapp. 1921. 52 pp. Price, 50 cents. Requests for bulletins should be addressed to the Director, Engineering Experiment Station, University of Washington, Seattle.