Meyen on the Vegetation of the Himalayali. 35 



Ave shall find that it corresponds to the region of the alpine 

 roses, or to that of shrubs in our mountain vegetation ; and that 

 it resembles the vegetation of the most southern portion of the 

 arctic zone in the vegetation of the plains. But the strong con- 

 trasts of the seasons with their great differences of temperature, 

 which occur in the northern zone, and the very equable tem- 

 perature of the lake of Titicaca, must naturally give rise to 

 very great distinctions in regard to the vegetation of the cor- 

 responding regions. The most important circumstance, how- 

 ever, in forming our estimate of the climate of the plateau of 

 Upper Peru, is the remarkable phenomenon, that there, the win- 

 ter, that is, the period from May to November, is not only the 

 dry season, but also the warm one ; while, in the real summer, 

 according to the position of the sun, that is, from November to 

 April, the wet, and, at the same time, the colder weather pre- 

 vail. During the latter hardly a day passes without rain, 

 and falls of hail and snow, which are so very rarely observed, 

 take place in November and December, the very months 

 which ought to be the hottest of the whole year. 



This extraordinary inversion of the usual meteorological rela- 

 tions produced by the position of the sun, is certainly a pheno- 

 menon well worthy of attention, not only for meteorology, but 

 also for the physiognomy of vegetation, and the social condition 

 of human society. It is evident that since the winter, ac- 

 cording to the position of the sun, is the dry season, the tempe- 

 rature at a particular place, owing to the constant clearness of 

 the heavens, and the consequent opportunity afforded for the 

 increase of heat by means of the sun's rays, must be much 

 higher than could belong to it according to general laws. On 

 the contrary, and this is of the greatest consequence for the ve- 

 getation, the summer is so much the colder, because, owing to 

 the constant rains and the evaporation of the fallen water, the 

 refrigeration of the air ensues ; and this chiefly|because the very 

 foggy atmosphere prevents the passage of the sun's rays. It is 

 also sufficiently well known, that at such great heights on the 

 mountains, whenever the influence of the sun is wanting, a very 

 low temperature is immediately the consequence. 



Thus, then, on the extensive plateau of Upper Peru, the 

 climate is in this remarkable manner altered to the prejudice of 



