1040 
the corresponding 7'-lines) and similarly the curves d = a and d = 2” 
(these curves are dotted). 
The curve (=o, T=), which forms the boundary between 
the region of the periodic and aperiodic conditions, is shown by a 
somewhat bolder line. This limit is of course found by equating the 
two roots of equation (26), ie. by putting £L*—=4M K or ay =H. 
Inside the aperiodic region the equation 
K dy Te M=—90 55) 
T == pa se . . = e . (55) 
holds or 
