van Rensburg and Andries Potgieter trek north. 1836 - James Alexander travels through Namaqualand . - The Great Trek has reached the Transvaal and the Free State areas. - Potgieter's trekkers defeat Ndebele at the Battle of Vegkop. 1837 - Piet Retief publishes his Manifesto. - Andries Potgieter and Piet Uys ,