Why did Sir Richard Burton doubt that Lake Victoria was the source of the Nile?

Sir Richard Burton’s skepticism regarding Lake Victoria as the source of the Nile stemmed from a combination of personal conflict, professional rivalry, and a commitment to rigorous exploration standards.

After the 1857–1858 expedition, during which Burton was incapacitated by malaria, his partner John Hanning Speke traveled independently to the lake and declared it the Nile's source. Burton, however, refused to accept this conclusion without further, definitive exploration. His doubt was fueled by several factors:

• Lack of Evidence: Burton believed Speke’s claim was premature and lacked sufficient geographical proof, leading him to publicly challenge the findings in his work, The Lake Regions of Central Africa (1860).12
• Personal Estrangement: The two men suffered a bitter falling out after Speke returned to London alone, where he was celebrated and funded for a second expedition while Burton was largely ignored and denied similar support.2
• Scientific Caution: Burton’s desire for further exploration was rooted in a desire for empirical certainty, which he felt was missing from Speke’s initial discovery.2