138 MR R. C. MOSSMAN ON 



inches, with a maximum of 18"54 inches in June and a minimum of 2"85 inches in 

 January. To the north of this wet zone the rainfall diminishes rapidly, while to the 

 south precipitation continues high. No reports are available for the 600 miles of coast 

 separating Ancud from Evangelists Island at the Pacific entrance to the Straits of 

 Magellan, where the annual rainfall is 111 "44 inches, with a seasonal distribution the 

 reverse of what obtains in the monsoonal region. 



At the island of Juan Fernandez, in lat. 33° 37' S., long. 78° 50' W., the distribution 

 of the rainfall through the months of the year is in harmony with that prevailing on 

 the Chilian littoral in the same latitude. The variation in the mean wind direction 

 shows, however, little change ; being south in the month of January, when this region 

 is well within the influence of the South Pacific high-pressure area, while in the 

 month of June, when the high-pressure belt is north of its summer position, the winds 

 at Juan Fernandez are south-west. These wind variations are also characteristic of 

 the ocean region to the east of this island. 



To the north of latitude 30° S. the monsoonal effect on the littoral becomes masked 

 or disappears ; but even at Caldera, in 27° S., the little rain that falls is precipitated 

 in the rainy season of the more southern stations. At Iquique, situated in 20° S., 

 where a shower of rain is of rare occurrence, the winters are much cloudier than the 

 summers ; the seasonal amount of cloud on the mean of the three years 1901-03 being 

 as follows : — 



Iquique. 



Cloud Amount 0-10. 



Years 1901-03. 





Hours of Observation 



8-2-9. 



Spring. 



Summer. Autumn. 



Winter. Year. 



6-4 



3-9 4-7 



72 5-5 



The indirect monsoonal effect would therefore appear to extend for some distance 

 into the northern rainless reo-ion. 



O 



There can be little doubt that the influence of the mountain chain of the Andes 

 in modifying the general circulation of the air is considerable, causing the coastal 

 winds to conform to the shores of the littoral, and to blow parallel with the main axis 

 of the Andean Cordilleras. The whole question clearly calls for a complete discussion 

 of all the available Chilian data, and the co-ordination and correlation of these data 

 with the observations from the Argentine Republic, Bolivia, Peru, and Brazil, as well 

 as the joining up of the land values with those given in various memoirs dealing with 

 the meteorology of the adjacent ocean regions. Among the factors bearing on the 

 causation of the monsoonal effect may be mentioned the seasonal migration of the 

 South Pacific anticyclone, the varying intensity of the high-pressure area in the north- 

 west of Argentina, and the fluctuations in the southern atmospheric cyclonic centres 

 of action in the Weddell and Bellingshausen Seas. The temperature gradient between the 

 hind and the ocean at different seasons will also have important bearings on the solution 

 of the whole question, and also variations in the temperature of the cold polar current 



