392 



Professor Sir James Dewar 



[Jan. 18, 



Black Development \n ^ 

 HANGING Bubble 





4 



^ Bctto-n cV Bm),U*-> 



(a) 



Black development .« 



BUBBLE POISED okRING 



p ^ 19 \^ 7p 7^ 3,t) 3^ ^ ^ ^0 



