374 



Professor Sir James Dewar 



[Jan. 18, 



to the camera. On a quarter-plate an exposure of 40 to 60 seconds 

 was necessary. A 9 by 7 inch Ross portrait lens was employed 

 at F. 11. Colour photographs of several of the columns have been 

 obtained in this way. 



Multiple Columns. 



Regular formations of greater complexity were obtained when 

 the bubble elements were reduced in size so that their diameters 

 were less than that of the nozzle. Thus, for example, two columns 

 which coalesced into one are shown in two perpendicular views in 



Fig. 11. 



Fig. 12. 



Figs. 9 and 10 (see also Fig. 24). The horizontal plane films l)e- 

 tween the successive elements of both columns were linked by a 

 " staircase" of films, inclined right and left at 120^ to the horizontal 

 films ; every bubble thus fitted into two bubbles of the adjacent half 



