- 5 - I 529 



is similar to that shown by "single-shot" photographs on stationary -fi tin given in a previous paper (i) 

 It is clear from the present photographs that the bubble is self-luminous for a period of the order of 

 a mill isecond. near its first minimum, the gas at the centre of the bubble being the first to become hot 

 enough to glow. It now seems probable that the patch of light seen in the centre of the bubble in the 

 •single-shot" photographs of the above mentioned paper (Figures 7d, e, f, - 8a, b, c, d, e, f, - 

 9a, b, c) is not light from the il luminat i/ig source passing through the bubble as suggested in that 

 paper, but the flash produced by the self-luminous bubble at its minimum, since in obtaining these 

 photographs the shutter was opened for a period including the first minimum. 



Reference . 



(l) photographic measurements of the size, shape and movement of the bubble produced by i oz. 



charges cf Polar Ammcn gelignite detonated underwater at a depth of 3 feet. 



