PHYSICAL FEATURES.—The coast land, of recent, and largely of deltaic, formation, is fringed in places by lagoons. Further inland, and covering a considerable part of Southern Nigeria, is an intermediate belt of clays, sandstones, and shales, which have built up a plain that rises in the north to a height of about 650 feet. Much of the remainder of Nigeria consists of crystalline rocks, which form open, undulating country, frequently broken by groups of rounded hills. Qn the left bank of the Niger, and along the upper and lower courses of the Benue, there are, however, considerable areas of sedimentary rocks, in which the rivers have cut narrow valleys, and to which they have, consequently, given a plateau-like formation ; while along the course of the middle Benue the Cretaceous rocks have weathered down into a great plain. In the north-east of the country there are alluvial plains which occupy a considerable part of the basin of Lake Chad.
CLIMATE.—In Southern Nigeria and in the lowlands of Northern Nigeria, the temperature is similar to that of the Gold Coast.
Lagos, for example, has an annual mean of 79° F., with a range from 75° F. in August to 81° F. in February and March ; and Zungeru one of 81•° F., with a range from 77° F. in August to 87° F. in March. On the upland districts conditions are somewhat more bracing, and in extreme cases the thermometer even falls below freezing point. Precipitation decreases from south to north ; and, while the coastal districts east of the delta of the Niger have a mean annual rainfall of 160 inches, the lands lying near Lake Chad, in the extreme north-east, have less than 20 inches.