MODERN GLASS — STOOKEY 335 



attenuation of sound waves is uniquely low. Thus, an electrical signal 

 can start a sound wave bounding around inside a specially shaped 

 piece of silica until the acoustic energy is needed to generate a second 

 signal. This high-purity silica glass is also transparent to the whole 

 optical spectrum from the vacuum ultraviolet (185 millimicrons) to 

 the near infrared, and is not discolored — as many glasses are, includ- 

 ing less pure silica — by exposure to high-energy radiation, so that it 

 is useful in special optical instruments employing light in the uv 

 range. 



