234 Proceedings of the Royal Physical Society. 



duration, and which are liable to occur at any season. The 

 " seca " of spring or summer, however, is the only one 

 dreaded, or even talked of, those of winter being compara- 

 tively harmless. Eain falls on an average 60 days in the 

 year. Gales of wind are very common, and there are few 

 days, except in summer, without wind sufficient to cause 

 annoyance when riding. The temperature does not fall 

 below freezing point above 20 days in the year, and hoar 

 frost may occur on other 20, but ice formed on the pools 

 during night melts in the morning. The average summer 

 temperature is 75°. 



The aspect of the country is at first somewhat monotonous, 

 consisting as it does of extensive plains, only varied by the 

 almost imperceptible elevations of the " cuchillas," or hills. 

 These plains or campos are smooth, and generally well 

 covered with herbage ; occasional rocks appear here and 

 there, especially along the ridges of the hills. The vicinity 

 is well watered, the rivers Eio Negro, and its tributary the 

 Carpinteria, nearly surrounding it, these again having 

 numerous smaller affluents, with permanent water. These 

 " arroyos," as the latter are called, expand here and there 

 into lagunas or lakelets, forming pleasant features in the 

 landscape. 



Although otherwise well clothed with vegetation, and in 

 their season with numerous wild flowers, the absence of 

 native trees is a marked feature not only of San Jorge but 

 of the whole campos of Central Uruguay, and one the reason 

 of which it is very difficult to explain, as trees when planted 

 seem to thrive well. The only woods are those which fringe 

 the rivers and water-courses, which they do from near their 

 source, increasing in breadth as the streams increase in 

 volume, until at length, here and there, on the larger of these, 

 they attain a width of from a mile to a mile and a half, and 

 in some places are quite thick and dark, affording a pleasant 

 shade, and a relief from the glare of the campo adjoining. 

 The trees, of which the species are many, are mostly stunted 

 and crooked, the willows being generally the tallest; there are, 

 however, places in which they grow comparatively tall and 

 straight. They are much valued for firewo^od and posts. 



