The cases that follow have been extracted from a larger sample where luminosity or power output data could be obtained. We have excluded some extreme cases (such as the Tunguska explosion of 1908 in Siberia) and all cases involving a single observer, leaving six adequately documented and researched incidents with multiple witnesses. In cases no. 2 and 3 the primary witnesses are known to the author, who has interviewed them personally. In case no. 4 the author has visited the site. In other cases we rely on the data assembled by qualified investigators, all of whom are known to us n1The author is particularly indebted to Dr. Claude Poher, Dr. Bruce Maccabee, Dr. Illobrand von Ludwiger and Mr. Jean-Jacques Velasco who made investigation reports available for this study..