John Hanning Speke questions about the height and extent of the lake could not be answered easily. Speke's eyes were still bothering him and he only saw a small part of the southern end of the lake and his view was blocked by islands in the lake so he could not judge the size of the lake well. However, Speke did estimate the elevation of Lake Victoria at 4000 feet by observing the temperature at which water boiled at that level. (This lake's being substantially higher than Lake Tanganyika did make it a more likely candidate for the source of the Nile.) From
John Kirk (explorer) William Carnegie Kirk was author of "A British Garden Flora". The engineer, Alexander Carnegie Kirk, was John Kirk's elder brother. From 1858 to 1864 Kirk accompanied the explorer Dr David Livingstone on the Second Zambezi Expedition as a botanist and experienced his work to end the East African slave trade. He found Livingstone an inept leader and in 1862 wrote "I can come to no other conclusion than that Dr. Livingstone is out of his mind and a most unsafe leader"". In 1866 Livingstone’s began his next and final expedition, to find the source of the Nile, from Zanzibar. From