The north and Phaleric walls were perhaps founded by Cimon, and were completed about 457 B.C. in the early administration of Pericles; the middle wall was built about 445 B.C. The lines of the north and middle walls have been ascertained from the remnants still existing in the 18th century and the scantier traces now visible.
It is the expression of the ultimate sovereignty of the people, and its existence gives to the working both of the Federal government and of the several state governments, a certain fixify and uniformity which the European, and especially the British, reader must constantly bear in mind, because under such a constitution every legislative body enjoys far scantier powers than in the United Kingdom and most European countries.
The temperature in the central part of the protectorate is much the same average as at the coast, but the range is far greater, varying from a shade minimum of 59° to a shade maximum of 107 0.1 The rainfall is much scantier on the plateaus than in the maritime regions, averaging in Northern Nigeria about 50 in.
In the mountains the flora is, naturally, scantier than in these two more favoured regions, but even here there is a rich variety.