CONTEMPORARY ADVANCES IN PHYSICS 



159 



best possible fit of such an expression to the data. He then noticed 

 that the same expression would equally well fit the data for the next 

 two of the depths, 153.5 and 105.2; and this convinced him that it is 

 physically sound. 



20 40 60 



80 100 120 140 160 180 200 220 240 



m 



Fig. 3 — Ionization ascribed to cosmic rays as function of depth beneath surface 

 of Lake Constance (the straighter curve is a semi-logarithmic, the other a direct plot) 

 (Regener). 



The ionization has therefore been separated by assumption into a 

 Restgang A and an effect of ionizing rays diminishing exponentially 

 with increase of depth. The value of A is 0.78; it is the downward 

 shift mentioned just above, so that the curve / in Fig. 3 shows the 

 part of the ionization ascribed to cosmic rays. The other curve 

 shows the logarithms of the ordinates of the curve /; the latter being 

 exponential, the former is straight; it is the close fit of this line to the 

 circles along its path (the logarithms of the data) that for the eye is 

 the most striking evidence for Regener's procedure. 



