188 



Professor Sir James Dewar 



[Jan. 19, 



"up to a liiindred times the thickness of the black supporting zone 

 above. The final collapse may have been associated with this con- 

 dition ; moreover, the potash soap is very sensitive to slight alkalinity 

 of the glass, — no other distnrbing canse was observed. 



Table 2 shows the lives of two sets of large bubbles under similar 

 conditions, in two vessels of 200-litre capacity ( Fig. 4). These vessels 

 were cylindrical glass globes, used in tlie Laboratory twenty-five years 

 ago in the production of liquid ethylene. They had short necks, 



Fig. 4. 



14 cm. diameter, which were fitted with good, cleansed india-rubber 

 corks to carry the blowing tubes, vetit tubes, etc. An oxidised steel 

 wire ring was used to support the majority of the bubbles. These 

 rings were about 12 cm. diameter, and were raised, by three supports 

 of the same oxidised wire, to about 25 cm. above the bottom of the 

 globe. For bubbles so supported the blowing tube was less than 

 1 cm. diameter ; it had a constriction of about 1 mm. bore, a few 

 centimetres above the lower end. A few drops of li(]uid from the 

 reservoir above were decanted down to fill the constriction for the 



