PRECIPITATION ON MOUNTAIN SLOPES POCKELS 99 



If now, by means of the Hertzian table, we determine the altitudes 

 at which condensation begins at the base curve o and for the curves 

 I, II, III, IV, then assuming the above given values 10 of t and F we 

 find the following results : 



I II III IV 



For the summer 930 1570 2730 4060 (5125) 



For the winter 600 2070 3100 4130 5100 



In the summer, according to this table, condensation will not 

 take place on the stream line IV, since its summit lies at the alti- 

 tude of 5100 meters; the summit of the clouds will, therefore, lie 

 a little below this. In the winter, the summit of line IV accidentally 

 agrees with the summit of the cloud. In the construction of the 

 cloud limit, introduced as a dotted line in fig. 3, and indicated by 

 5 for summer and W for winter, we have also used the lines of flow 

 midway between o and I, and I and II, respectively. 11 



We can now, with the help of the Hertzian table, easily find the 

 quantity of water condensed in every kilogram of moist air as it 

 progresses along any one of the lines of flow that we have constructed , 

 either in its totality or as it passes successive vertical lines : we thus 

 attain the folloiving values of the total condensation: 



Curve I II III 



For the summer 2.85 2.42 1.22 0.26 grams. 



For the winter 1.5 0.74 0.34 0.14grams. 



Let g x (h) be the quantity condensed up to the abscissa x when 

 moving along that line of flow whose initial point is at the altitude 

 h, and let H be the initial altitude of that line of flow which at the 

 given abscissa x intersects the upper cloud limit; moreover, let u' 



10 From the above numbers it follows that an elevation of any kind of 

 less than 500 meters will not give occasion for condensation under average 

 atmospheric conditions, neither in summer nor in winter. In the summer, 

 for a mountain altitude of between 600 and 800 meters, a cloud will form 

 between the altitudes 1000 and 3000 meters, but will not touch the moun- 

 tain; it is only for greater mountain heights that the cloud will rest on the 

 mountain. 



11 In an analogous way for the first example, where we have assumed a 

 plateau-like mountain of 900 meters altitude, we find a region of cloud which 

 for the average summer conditions begins at 40 meters below the summit of 

 the plateau and reaches up to over 3000 meters; but in winter, on the other 

 hand, it begins at 500 meters above the valley and rises up only about 700 

 meters above the mountain top; therefore, in this season it covers the moun- 

 tain like a flat cap. 



