A Further Note on the Diurnal Variation of Level at Kimherley. 77 
This arrangement gives the same values for the average daily swing of 
the pendulum, but it shows a smaller range of earth temperature on cloudy 
days, and a greater range on clear days than the arrangement of Table 4. 
On the other hand, it shows more sunshine on the cloudy days and less 
on the clear days than that Table does. 
It seems to follow from this relation between the diurnal oscillation of 
level (as shown by the horizontal pendulum), the duration of sunshine, 
and the range of temperature of the surface soil, that if the oscillation is 
of photo-electric origin then it must depend upon the energy of waves of 
fairly long wave-length, i.e., upon waves that are effective as heat rays 
rather than upon the more strictly actinic rays. 
t 
