160 



THE ANDES OF SOUTHERN PERU 



tions from here down to the plains all show that there is a distinct 

 change in wind direction in sympathy with the larger features of 

 the topography, especially the deep valleys and canyons, the trades 

 coming in from the northeast. 



CLOUDINESS 



It will he seen that the sky was overcast or a fog lay in the 

 valley 53 per cent of the time at early morning hours. Even at 

 noon the sky was at no time clear, and it was more than 50 per 

 cent clear only 18 per cent of the time. Yet this is the so-called 

 "dry" season of the valleys of the eastern Andes. The rainfall 

 record is in close sympathy. In the 79 days' observations rain is 

 recorded on 50 days with a greater proportion from mid-Septem- 

 ber to the end of the period (November 6), a distinct transition 

 toward the wet period that extends from December to May. The 

 approximate distribution of the rains by hours of observation 

 (7 a. m., 1 p. m., 7 p. m.) was in the ratio 4:3:6. Also the greatest 

 number of heavy showers as well as the greatest number of 

 showers took place in the evening. The rainfall was apparently 

 unrelated to wind direction in the immediate locality, though un- 

 doubtedly associated with the regional movement of the moist 

 plains air toward the mountains. All these facts regarding 

 clouds and rain plainly show the location of the place in the belt 

 of maximum precipitation. There is, therefore, a heavy cover of 

 vegetation. While the situation is admirable for defence, the 

 murky skies and frequent fogs somewhat offset its topographic 

 surroundings as a lookout. 



ANALYTICAL TABLE OF THE STATE OF THE SKY, MACHU PICCHU, 1912 





Morning 



Total 



Noon 



Total 



Kvening 



Total 





Ang.- 

 Sept. 



3.0 

 12.0 

 4.0 

 6.0 

 3.0 



Oct.- 



Nov. 



14.0 

 3.0 



10.0 

 4.0 

 1.0 



Days 



% 



Aug.- 

 Sept. 



Oct.- 



Nov. 



Days 



% 



Aug.. 

 Sept. 



Oct.- 

 Nov. 



Days 



% 



FoffffV 



17.0 

 15.0 

 14.0 

 10.0 

 4.0 



28.4 

 25.0 

 23.3 

 16.7 

 6.6 



1.0 



6.0 

 9.0 

 5.0 

 0.0 



8.0 

 7.0 

 2.0 

 0.0 



1.0 



14.0 



16.0 



7.0 



0.0 



2.6 



36.8 



42.2 



18.4 



0.0 



1.0 

 13.0 

 8.0 

 9.0 

 3.0 



2.0 



11.0 



15.0 



4.0 



3.0 



3.0 

 24.0 

 23.0 

 13.0 



6.0 



43 



Overcast 



34 8 



50-100% cloudy 



0-50% cloudy 



Clear 



33.3 



18.8 

 88 







