The combination of towering mountains, burning deserts, and malarial swamps proved to be a formidable barrier, and it was difficult to gain a foothold on the coast The conquest of India was completed; Australia and New Zealand were settled; many islands of the Pacific passed under the British flag; and England extended her influence into many parts of Africa. France had begun the conquest of Algiers in 1830 and had pursued in leisurely fashion the subjugation of that difficult country. The forest gives way slowly as the traveler approaches the savanna country, the third geographical region of Nigeria. The great river from which the country takes its name is another important physical feature of Nigeria. Climate has been a factor of fundamental importance in the history of British enterprise in Nigeria. Both Christianity and Mohammedanism claim adherents among the Yorubas, but the majority remain pagan.