20 Alexandkk G. Ruthven 



tempered on the north coast by the trade winds and sea breezes, but are 

 very hot on the west and south sides during most of the year. Ascending 

 the mountains, the temperature gradually lowers. Between 4,000 and 5,000 

 feet is an ideal climate, having a minimum temperature of about 60° F. 

 and a maximum of 80°, where an open fireplace is a great comfort at times 

 and woolen clothing almost a necessity, especially during the rainy season 

 from 5,000 feet upwards. When 8,000 feet is reached the minimum drops 

 to an average of about 54°, and it is always chilly in the shade, while in 

 the open the direct sun's rays are blisteringly hot around midday. At 9,000 

 feet, or a little above, the mercury drops to 46° F. The above temperatures 

 are taken from San Lorenzo, and are from 4° to 5° higher than at corre- 

 sponding elevations on the western slopes of the main Sierras. The frost 

 line varies with the season and the exposure, but is probably somewhere 

 near 11,000 feet. The lowest average limit of snow is somewhere near 

 16,000 feet, rising on the southern exposures during the dry season to 

 17,000 or even 17,500 feet, and dropping down to 15,000 in the sheltered 

 valleys of the north slope. There are times during the dry season when 

 heavy falls of snow occur as low as 13,000 feet, but this snow never lasts 

 more than from twenty-four to forty-eight hours, usually falling during the 

 night and melting during the following day. On the north slopes of the 

 mountains there is a far greater humidity and lower temperatures than on 

 other slopes at corresponding elevations. The climate at Pueblo Vie jo 

 (2,000 feet) approximates that of 4,000 feet on San Lorenzo and the west 

 slopes, while that of San Miguel (5,500 feet) corresponds closely with that 

 of the Cerro Quemado de San Lorenzo, which has an elevation of 8,000 

 feet. These differences in conditions on the north slopes apparently exert 

 a powerful influence on plant and animal life on that side, causing a cor- 

 responding descent in altitudinal distribution. At Don Diego the heavy 

 mountain forest extends down to the very edge of the narrow coastal plain, 

 and the upper foothills fauna descends with it, literally squeezing out the 

 lower foothills forms from this region or forcing them to mingle with those 

 of the coastal plain fauna below. 



There are two distinct and well-marked seasons, the rainy and the dry, 

 the former covering the months of April to November, inclusive, over the 

 greater part of the mountains from 3,000 feet upward. Below 3,000 feet 

 the seasons -of rain are retarded or extended by local conditions. On the 

 northern side, from the Rio Frio around to the Rio Piedras, the rains do 

 not begin before May or June, and usually are over by the end of October, 

 while on the north side, from the Rio Piedras to beyond Dibulla, they begin 

 as early as March, and often continue as late as the end of December. Even 

 during the dry season the north exposure of the Sierras is refreshed by 

 almost daily fog banks, caused by the condensation of the moisture carried 

 by the trade winds, w^hen they come in contact with the cool vegetation of 

 the mountain slopes. The great southern exposure of the Sierras receives 

 a much smaller amount of moisture than any of the other portions, which 

 is divided into two periods, at least in the lowlands and foothills, much 

 resembling the seasons of the interior of Colombia. The spring rains fall 



