SL>0 



Professor Sir James Dewar 



A is the charcoal tube about 7-8 mm. diameter and about 25 cm. 

 lon^, for convenience of standing in a deep vacuum vessel in order 



Fig. 20. 



to remain umlistur])L'fl in liquid air for extended periods. A is 

 • ■nlarged to a bull* below sufficient to contain a o-ram or two of good 



