p depression which crosses Honduras
from Puerto Cortez to the Gulf of Fonseca, the strike is commonly from
north to south. The depression is probably a "Graben" or trough formed
by faulting.

The great volcanoes of Mexico and Central America stand upon the
Pacific side of the continent, and it is only where the land contracts
to a narrow neck that their products spread over to the Caribbean
shore. The extent of the volcanic deposits is very great, and over a
wide area they entirely conceal the original structural features of
the country. The eruptions began towards the close of the Cretaceous
period and continue to the present day. The rocks are lavas and ashes,
chiefly of andesitic or basaltic composition, but rhyolites and
trachytes also occur, and phonolite has been met with in one or two
places.

According to R.T. Hill, there is but little geological evidence of any
Tertiary or later connexion between the Caribbean Sea and the Pacific,
excepting, perhaps, a shallow opening during the Eocene period. It
should, however, be stated that all authorities are not agreed upon
this point, and K. Sapper found marls and sandstones which he believes
to belong to the Upper Tertiary, lying horizontally at a height of
about 7500 ft. in the Mexican state of Chiapas. Unfortunately the
fossils obtained from these beds were lost.

_Climate_.--The climate of Central America is subject to the most
marked local differences of heat and cold, owing partly to the
proximity of two oceans, partly to the variations of altitude which
render such territories as the swamps of the coast, or the lowlands of
British Honduras and northern Guatemala, totally unlike the alpine
regions of Salvador and Costa Rica. The whole area may, however, be
roughly divided into a tropical zone (_tierra caliente_), from
sea-level to about 1500 ft.; a temperate zone (_tierra templada_),
from 1500 to 5000 ft.; and a cold zone (_tierra fria_), above 5000 ft.
These figures are, of course, only approximately correct; and it often
happens that, at the same elevation, the heat is greater on the
Pacific than on the Atlantic versant. The rainy season on the Pacific
slope varies in duration from four to six months, between April and
December. It lengthens as the altitude increases. On the coast, it
corresponds with the prevalence of the south-west monsoon, the
tempestuous _Cordonazo de San Francisco_,