CONTEMPORARY ADVANCES IN PHYSICS 



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Though the work of MilHkan and his school is unrivalled for 

 extent, I will begin with Regener's, which is an unique example of a 

 wide range of water-depths covered in a single experiment. The 



y 



Fig. 1 — Sketch of a two-fibre electroscope (after Millikan). 



ionization-chamber (walls of steel a centimeter thick, 39 liters (!) in 

 volume filled with carbon dioxide at a pressure of 30 atmospheres) 

 was floated for days at a time at each of several levels in the great Lake 

 of Constance (Bodensee) on the northern boundary of Switzerland. 

 Every hour a light flashed for a few seconds, and the image of the 

 fibre of the string-electrometer was impressed upon a film, wound about 

 a slowly and equably revolving drum. One sees in Fig. 2 the succes- 

 sive images of the string, developed after the experiment was completed 

 and the film removed from the drum; it is evident how they lie closer 

 together as the chamber is lowered deeper and deeper beneath the 

 surface, the ionization therefore becoming feebler and feebler. The 



