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 Hanning Speke variety of tropical diseases once they went inland. By 7 November 1857 they had traveled over 600 miles on foot and donkey and they reached Kazeh (Tabora), where they rested and recuperated among Arab slave traders who had a settlement there. In Kazeh Burton became gravely ill and Speke went temporarily blind as they travelled further west. After an arduous journey, the two arrived in Ujiji in February 1858 and became the first Europeans to reach Lake Tanganyika (although Speke was partially blind at this point and could not properly see the lake). They decided to explore the lake but