tropical zone

The tropical zone, which extends 23° 27′ from one part to the other of the equator.

Granite abounds in the tropical zone, and seems to prefer chains of moderate elevation.

The plant is a native of India, but is now widely spread throughout the tropical zone.

In the course of about a week the temperature fell, for we were steadily approaching a less tropical zone.

Below, the valley is fertile and covered with vegetation, first of the temperate and then of the tropical zone.