VL —THE FREQUENCY-DISTRIBUTION. 193 
at the ends of the range and a minimum towards the centre. 
The ideal form of the distribution is illustrated by fig. 18. 
F16. 18. —An ideal Distribution of the U-shaped Form, 
This is a rare but interesting form of distribution, as it stands 
in somewhat marked contrast to the preceding forms. Table XV. 
and fig. 19 illustrate an example based on a considerable number 
of observations, viz. the distribution of degrees of cloudiness, or 
estimated percentage of the sky covered by cloud, at Breslau 
TABLE XV. —Showing the Frequencies of Estimated Intensities of Cloudiness 
at Breslau during the Ten Years 1876-85. (See ref. 2.) See Fig. 19. 
Cloudiness. Frequency. Cloudiness. | Frequency. 
71 21 
b 71 
L7 194 
: 117 
2089 
"tal -9 
lis 
265.