I remember that, growing up in Namibia (South West Africa in those days), a few articles appeared from time to time in the local papers about expeditions into the Kalahari to try and find the lost city of the Kalahari. There are also other references to other ‘lost cities’ of the Kalahari, especially that of Dr Dierks.
I also notice that, according to the map by Farini, they stuck mainly to the Bechuanaland (Botswana side) of the Kalahari. The following is not directly linked to Farini's trip, but more information on what happenedin the area in the years after his travels.

Photo of Swartmodder with the wall built in those years to keep out the animals.
There are also three references to 'Zwartmodder' on Farini's map and in one reference in the story. During the 1880's to 1906 this area had a very rich, but also violent history. This was when Hendrik Witbooi (image of him on current Namibian Dollar notes) and his family moved from Pella in the Northen Cape to Namibia and the Gibeon area and a few white settlers also settled in this area next to the Auob river (currently Stampriet).
In October 1904, Izak Wibooi, Hendik's brother was the initiator of a campaign to rid the area of all Afrikaans and German speaking white men. On 10 October 1904 Izak witbooi was in charge of a party who murdered all the male members on the farm Zwartmodder, except for Dirkie Smit who was 2 years at that stage and was dressed in a gown and the Nama soldiers thought that he was a girl. Another boy of about twelve also survived for a few days. He was wounded and when shot fell to the ground unconscious. When they piled up the bodies he came by and was spared. Apparently he died later of his wounds. The body of the owner of the farm, Hendrik Smit was left where he was gunned down next to the swartmodder fountain. All the women was put on ox wagons and taken to were taken to Rietfontein and returned to Cape Town. They later returned to Swartmodder to bury their loved ones. You will see in the photos that all but Hendrik Smit was buried in the same grave as their remains still were in one pile.

Graves of Hendrk Smit and the other males of Swartmodder

Dirkie Smit, the sole male survivor of the massacre
Hendrik Witbooi was killed in the following military campaign between the Namas and the German forces in October 1905 at Vaalgras near Koichas. After his death the German military forced most of the Namas who refused to surrender from Namibia into Bechuanaland in the Kgalagadi area.