Air engine tester. Dr. K.C. Dickinson, Chief of the Heat and Power Division of the Bureau of Standards, and the control room of the new aircraft engine testing laboratory at Arlington, Virginia Here all engines for use on licensed airplanes are to be tested and to protect the observer, the control room and the room in which the engines are mounted are heavily reinforced with concrete to prevent flying engine parts striking the observers

The Harris & Ewing, Inc. Collection of photographic negatives includes glass and film negatives taken by Harris & Ewing, Inc., which provide excellent coverage of Washington people, events, and architecture, during the period 1905-1945. Harris & Ewing, Inc., gave its collection of negatives to the Library in 1955. The Library retained about 50,000 news photographs and 20,000 studio portraits of notable people. Approximately 28,000 negatives have been processed and are available online. (About 42,000 negatives still need to be indexed.)