To return again to South Africa—British rule brought about a great development in exploration. Campbell, a Scotch missionary, in 1812 laid down the course of the Orange river on the map and discovered the source of the Limpopo. Captain (afterwards General Sir J. E.) Alexander made an interesting journey overland from Cape Town to Walfish Bay; Dr William Burchell and Captain William Cornwallis Harris[172] explored Bechuanaland and the Transvaal, and added much to our knowledge of the great African fauna. Robert Moffat and other missionaries extended our knowledge of Bechuanaland; Angas investigated Zululand; Major Vardon explored the Limpopo. In the first decade of the 19th century Henry Salt (formerly British Consul-General in Egypt) explored Abyssinia and the Zanzibar Coast. In 1822 Captain (afterwards Admiral) W. F. W. Owen left England with two ships, and spent four years exploring the East and West coasts of Africa, and the island of Madagascar. He especially added to our knowledge of Delagoa Bay and its vicinity. He despatched vessels on the first voyage of discovery up the Zambezi, which unhappily ended in the death of all the British officers. The limit reached was Sena. The East and West coasts of Africa were charted by Captain Owen with the first approach to real accuracy. Although he was not an overland explorer, his voyage marks a most important epoch in African discovery, and many of his surveys are still in use. Mungo Park and others having entertained the idea that the Niger might find its ultimate outlet to the sea in the river Congo, an expedition was sent out in 1816 to explore the lower Congo. It was a naval expedition, of course, and the command was given to Captain Tuckey. He surveyed the river to the Yelala Falls, and carried his expedition inland to above these rapids near the modern station of Isangila. Unfortunately, he and nearly all the officers of his expedition died of fever; but his journey, being conducted on scientific lines, resulted in considerable additions to our knowledge of Bantu Africa, its peoples, languages, and flora.