1917.] Chapman, Distribution of Bird-life in Colombia. 81 



mean temperatures are derived from observations made on distinct systems, 

 but as a rule the temperature of the earth, in a part sheltered from the sun 

 and rain, at a depth of 30 inches from the surface of the ground, will repre- 

 sent in these latitudes the mean temperature of the locality. In tropical 

 regions, where vegetation is not exposed to great variations of temperature, 

 the most important point to which the agriculturist should look is the mean 

 temperature, if he would judge correctly of the climate of any locality. 



"Table of Mean Temperatures in the U. S. of Colombia, between 2° and 6° N. 

 Lat., compiled from observations by Humboldt, Caldas, Boussingalt, Mosquera, 

 Reiss, Stubel, and White. 



"The mean in the greater altitudes varies somewhat according to the 

 greater or less extent of snow-covered mountains, and in the lesser altitudes 

 the temperature is affected by the open or inclosed character of the valleys 

 and by the presence or absence of vegetation. Generally, however, it will 

 be found that the above means are suiBciently near the truth to be of 

 practical utility." 



Rainfall: — As before remarked, the seasons in Colombia are charac- 

 terized by dry and wet periods rather than by variations in temperature. 

 It is, therefore, to be regretted that data in regard to rainfall are even less 

 satisfactory than those relating to temperature. Furthermore, variations 

 in rainfall, both at the same locality and at neighboring stations, are so 

 great that the statistics available merely demonstrate the need for additional 

 observations before even the most conservative generalizations can be made 

 on this branch of Colombian meteorology. 



Two types of the seasonal distribution of rain are commonly recognized 

 in Colombia. In one, a wet season of six months duration is followed by a 

 dry season of equal length. In the other, wet seasons each of three months 

 duration are separated by dry seasons of equal length. 



