From Flickr: “Variable Density Wind Tunnel” by NASA on The Commons

Description: Left to right: Eastman Jacobs, Shorty Defoe, Malvern Powell, and Harold Turner. In this photo taken on March 15, 1929, a quartet of National Advisory Committee for Aeronautics (NACA) staff conduct tests on airfoils in the Variable Density Tunnel. (In 1985, the Variable Density Tunnel was declared a National Historic Landmark.)

Center: LARC
Image # : L-3310
Date: March 15, 1929

via Flickr