The discovery of interior part of Africa did not take place, why?

1)       To the middle of the 19th century, the westerners did not have any idea of the interiors having dense forests, big lakes, perennial rivers and large tracts of desert in the African Continent.
2)       However, the composition (art) of Africa was not known to the world at large.
Therefore, sufficient attempts were not taken at discovering the interior of the African continent