GEOLOGY OF GUATEMALA AND SPANISH HONDURAS 511 
Rainfall and humidity have everywhere an important bearing 
on vegetation and therefore on surface features. The high plateaus 
behind mountains which catch all the moisture suffer from aridity 
and afford scant vegetation. At lower elevations, but again in the 
lee of the mountains, there are deserts, as at Zacapa, supporting 
only cactus. . Near the sea both coasts receive an overabundance 
of rainfall with accompanying great humidity. On both sides of 
the Isthmus the northeast trades are the prevailing winds, but on 
the Pacific Coast the winds are variable except during winter of the 
northern latitudes. 
Statistics for an average year show rainfall on the Pacific Coast 
(elevation 600 feet) of 240 inches; at Guatemala City (elevation 
4,900 feet) of 60 inches; at Quirigua (elevation 240 feet), 57 miles 
from Puerto Barrios, but behind a mountain range, of g9 inches; at 
Panzos (elevation 50 feet), roo miles inland, of 115 inches; at 
Puerto Barrios, on the Atlantic, of about 200 inches. The rainy 
season on the Pacific Coast is May 15 to October 15, on the Atlantic 
Coast June 15 to August 15 and September 15 to February 15. 
The best weather in Guatemala and Honduras as a whole is there- 
fore in the winter and spring of the northern latitudes, and only 
during this dry season can geologic work be carried on satisfactorily 
in the coastal regions. 
GEOLOGY 
Spanish Honduras.—Northern Honduras consists of two 
mountain ranges of the metamorphic series, each with many 
subsidiary branches. The first of the parallel ranges forms a por- 
tion of the boundary line between Guatemala and Honduras (Figs. 
t and 4) and.is variously known as the Sierra de la Grita, Sierra de 
Merendon, Sierra del Espiritu Santo, and the Sierra de Omoa—the 
Omoa Mountains. This range lies for a distance between the 
Motagua and Chamelecon rivers (Fig. 2), but east of the broad 
Chamelecon-Ulua lowlands it reappears in Punta Sal and in the 
Bay Islands (Utilla, Ruatan, and Bonacca). ‘The second range, 
Sierra de Pija (Fig. 1), lies west of the Ulua River between the 
various short streams on the Atlantic shore and the Aguan River 
(Yoro-Olanchito) valley. This range extends into the sea east of 
Trujillo. 
