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suffering from pulmonary diseases, and complaints aflf'eeting the 

 heart and liver, anticii):ite the month of August (midwinter) with 

 consternation; and their anxiety is not quieted until they have 

 passed through the dreaded ordeal. 



While passing the winter in San Juan, I noted the courses of 

 upwards of twenty zondas. Some were of short duration ; 

 others lasted eighteen or twenty hours. 



During the latter part of August, 1855, while standing upon 

 the saline desert, a few miles east of San Juan, my attention was 

 attracted to a cloud of dust that appeared to roll through the air 

 as it appi'oached me. I started for a sheltez", and had hardly 

 reached it, when the zonda swept past, filling the air with fine 

 yellow sand. The temperature of the previously sultry atmos- 

 phere suddenly rose many degrees, and the occupants of the 

 neighboring huts were affected with severe headaches. 1 noted 

 with a compass the course of the wind, and found it to be 

 west. All night, and through the following day and night, it 

 continued blowing with undiminished force. Each hour the 

 vane beside the hut was consulted, and the same course as at 

 first was always observed. A few hours before the wind 

 ceased the sand showers were exhausted. The greatest heat 

 was during the first few hours : and this is always the case, 

 whether the zonda commences during the daytime or night. 

 After continuing for thirty-six hours, the change came. It was 

 instantaneous. The hot wind seemed cut off at right angles by 

 a cold wind from the south. The change could not have occu- 

 pied more than forty seconds. The south wind lasted twenty 

 hours, and was as violent as the hot zonda. In speaking of the 

 Mendoza zondas, Miers does not mention the succession of the 

 south wind. It is easy to comprehend that after so large a 

 space has become filled with heated air, the effect will be felt 

 in the cooler regions of the south, and a strong current from 

 that direction will rush in to restore the atmospheric equilibrium. 

 Hence the cause of the south wind succeeding the zonda. 



Miers believed that the origin of the zondas was volcanic, 

 and for a precedent, I will state, upon the authority of Sir 

 Woodbine Parish, that the volcano Penquenes, which is situated 

 about one hundred miles southwest from Mendoza, and reaches 

 an altitude of nearly fifteen thousand feet above the level of the 



PROCEEDINGS B. S. N. H. — VOL. VI. 14 AUGUST, 1857. 



