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
Jakob Erhardt then in the "Church Missionary intelligencer" in 1856. The map was reproduced with commentary in other publications. The reports of snow on mounts Kilimanjaro and Kenya, near to the equator, caused considerable controversy. The map caused the British government and the Royal Geographical Society to hire Richard Francis Burton and John Hanning Speke to investigate the great lake, or lakes, and determine if they were the source of the Nile. The map came to be known as the "slug map" from the shape of the Uniamesi or Niassa inland sea. Burton called it the Mombas Mission Map. Erhardt worked in