26 LABORATORY EQUIPMENT AND APPARATUS FOR TEACHING ENGINEERING SUBJECTS-NAMELY, EQUIPMENT FOR TESTING LOAD, STRESS, AND STRAIN OF MECHANICAL STRUCTURES SUCH AS TRUSSES, BEAMS, AND THE LIKE, AND THE MATERIALS OF WHICH SUCH STRUCTURES ARE MADE; FLUID FLOW DEMONSTRATION AND EXPERIMENTAL APPARATUS; ANALOG FLUID CIRCUIT SIMULATOR; AND POLARISCOPE APPARATUS FOR DETERMINING AND OBSERVING STRESS