I viewed the test, with the Coordinating Committee expedition, from a point about twenty miles away.  At the instant of the explosion I was looking directly at it, with no eye protection of any kind.  I saw first a yellow glow, which grew almost instantly into an overwhelming white flash, so intense that I was completely blinded.  There was a definite sensation of heat.  The brilliant illumination seemed to last for about three to five seconds, changing to yellow and then to red; at this stage it appeared to have a radius of about twenty degrees.  The first thing I succeeded in seeing after being blinded by the flash looked like a dark violet column several thousand feet high.  This column must actually have been quite bright, or I would not have been able to distinguish it.  By twenty or thirty seconds after the explosion I was regaining normal vision.  At a height of perhaps twenty thousand feet, two or three thin horizontal