Polyglotta Africana is a study written by the German missionary Sigismund Wilhelm Koelle in 1854 in which he compared 156 African languages (or about 120 according to today's classification; several varieties considered distinct by Koelle were later shown to belong to the same language). As a comparative study it was a major breakthrough at the time.
Koelle based his material on first hand observations, mostly with freed slaves in Freetown, Sierra Leone. He transcribed the data using a uniform phonetic script devised by the Egyptologist Karl Richard Lepsius. Koelle's transcriptions were not always accurate; for example, he persistently confused [s] with [z] and [tʃ] with [dʒ]. His data were consistent enough, however, to enable groupings of languages based on vocabulary resemblances. Notably, the groups which he set up correspond in a number of cases to modern groups: