Among these lavas is the "pipe" amygdaloid of which many blocks have been transported great distances down the Vaal river.
Flowing between steep banks, considerably below the general level of the country, here about 3000 ft., it receives, between the Vaal confluence and the Atlantic, a distance of more than 400 m.
In the neighbourhood of the Vaal, confluence, where the river passes through alluvial land, and at some other places, the waters of the Orange are used, and are capable of being much more largely used, for irrigation purposes.
Mission stations north of the 'Orange were established a few years later, and in 1813 the Rev. John Campbell, after visiting Griqualand West for the London Missionary Society, traced the Harts river, and from its junction with the Vaal followed the latter stream to its confluence with the Orange, journeying thence by the banks of the Orange as far as Pella, in Little Namaqualand, discovering the great falls.
It is built by the banks of a tributary of the Vet affluent of the Vaal, and is a trading centre for a large grain and pastoral district.