IPHYSICAL GEOGRAPHY AND BOTANY OF CHILI. 107 



The wind is very strong in the day-time on the mountain tops, 

 so strong that it is considered prudent to cross early in the 

 morning, as towards midday it is sometimes almost strong enough 

 to blow over man and horse. I cannot positively affirm that such 

 a thing has ever occurred, but I think it a very possible event. 



Once I was crossing the side of a ridge of frozen ground, so 

 steep that one false step would rolled me down some thousand 

 feet into a torrent of ice -water below ; I was on horseback, and so 

 benumbed with cold that I could not venture across on foot ; 

 when a sudden gust of wind actually stopped my horse, and blew 

 my poncho over my head so as completely to blindfold me. The 

 only thing I could do, was to remain motionless and blindfolded 

 until the gust had passed. This might have been half a minute 

 but it appeared to me about an hour, during which time my 

 horse, evidently understanding our danger, stood trembling in 

 in every limb. This incident will give some idea of the force of 

 the wind in these high places, and its importance with regard to 

 the perpetual snow -line. The slope of the ground must also be 

 taken into consideration. 



Probably the heat of the sun is the principal cause of the 

 retention of snow on the mountains, for when the snow has been 

 well ground into small fragments by the wind the top is slightly 

 thawed by the sun, and the water so formed trickles into the 

 interstices, and freezing forms a solid mass. I do not know any 

 English name for the mass so formed. The French call it "neve.^^ 



As may easily be imagined, the cold dry air descending from 

 the Andes greatly modifies the climate of the central plains. 



Then the coast is washed by a cold stream from the Antarctic 

 Ocean, Humboldt's current, which greatly reduces the tempera- 

 ture on the coast, so that our climate is not as warm as its 

 geographical position would seem to give it. 



The height of the Andes also affects the rainfall, by breaking 

 the force of the east winds, and depriving them of a large amount 

 of moisture. The following table will give an idea of the 

 temperature and annual rainfall : — 



