On the map, several subtle but interesting things can be discovered, including, in the northeast section of the cartograph, a reference to a stream flowing into Lake Victoria, then known by the missionaries as the Ukerewa. A note describes how the waters of the stream were very sweet, but stained the teeth a sickly yellow. This note is probably the first known text referring to the drinking water, found primarily around Mount Meru, which has a high content of fluorine and causes a yellow-brown stain to the incisors which cannot be removed.