Smithsonian Report, 1951. — Laufer 



PLATE 3 



1. Five solid glass marbles suspended in space b\ sound waves from a high-intensity ultra- 

 sonic siren which are beamed against a reflecting board. Courtesy Harold K. Schilling, 

 Pennsylvania State College. 



2. IVansmission of a wide ultrasonic beam through aluminum wedges of increasing taper. 

 Transmission occurs only where the wedge thickness is such as to give internal resonance. 

 Courtesy Bell Laboratories Record. 



