CLIMATE. 
lands to the Pacific plain, with irresistible force; especially 
when, from meeting with the wind off the Pacific, an eddying 
current is produced. 
On the shores of the Pacific these northers are also strong, 
and carry with them clouds of dust and fine sand from the 
plains. As they blow off shore, the sea is but little disturbed 
by their influence, and vessels would doubtless lay in perfect 
security during the hardest gales. There is thus a free circula- 
tion of air across the whole Isthmus, sweeping through the val- 
ley of Chicapa, and carrying the cool air of the north across 
to the Pacific shore. 
The prevalent winds which blow upon the Isthmus come 
from a northerly point for the reason stated — i. e., the influence 
of the Gulf Stream : they are augmented in force and frequency 
by the course of the sun over these latitudes. The solar rays, 
playing upon the heated waters and land, warm the contiguous 
air, which immediately rises upwards into the higher regions, 
and is replaced by a current of cool air, which comes down from 
the north to fill the vacuum. These winds, blowing from the 
north so long as the sun is travelling over these latitudes, are 
termed northers, and are always loaded with watery vapor^ be- 
ing saturated by the evaporation of the sea. 
The following figures show the number and direction of the 
winds, observed by the officers of the survey and by those of the 
United States Navy, on the northern side of the Isthmus. Thus 
in 104 observations made daily, there were 
Winds from N 19 days or 
« N. E. & N. N. E. 36 " Northerly winds 69 
* " N. W 14 « Southerly 31 
" « S 12 " 
" S. E 13 « Easterly 49 
" S. W 6 « Westerly 24 
« « W 4 « 
104 
The prevalence of northerly winds is here well shown, and their 
effects upon the temperature and productions of the Isthmus 
are well marked. 
Between the tropics the rains follow the sun, and when he is 
north of the equator, the rains prevail in the northern tropic. 
