File:The Quarterly journal of the Geological Society of London (12733577955).jpg

0E DIAMONDS IX SOUTH AFRICA. 59
were found in this drift. Some localities have yielded immense
quantities, as Pniel, Klipdrift, &c.
The newer one, or " recent " drift, occupies the present river-
bed. It differs in composition from the older drift, in containing a
larger percentage of sandstone pebbles and pebbles of soft rocks.
Its general colour is greyish, while the older drift is of a reddish
colour. The newer drift contains the same well-rounded polished
pebbles of agate &c. as the older one.
Diamond-workings have been successfully prosecuted for a conside-
rable distance along the Vaal river. In the newer drift " Cawood's
Hope" was an unusually rich digging; while "Waldeck's Plant yielded
the largest diamond yet found in S. Africa

its weight is 288 carats.
The gems found in the drift-workings are of finer quality, and
invariably command a higher price than those obtained from the
various " dry diggings."
A very extensive development of " glacial conglomerate " spreads
over the country along the course of the Orange River, west of
Hope Town (lat. 29° S.). Further west it leaves the river to the
north, and spreads as a belt through Bushmanland. Isolated tracts
occur near Beaufort West.
At Prieska, on the Orange river, diamonds were found in this
conglomerate. Several have been found on its surface between
Prieska and Hope Town, notably the " Star of S. Africa."
Systematic search is not likely to meet with much reward in the
case of this conglomerate, as the very nature of its formation forbids
the hope of diamonds being thickly distributed in it.
Many of the hard boulders are scored and scratched in such a
manner as to leave no doubt concerning its origin.
That the wind has acted as an agent in the distribution of dia-
monds, though perhaps of small ones only, is clearly proved by their
occurrence in the drifting sandy soil at Du Toit's Pan. It has, no
doubt, been the means by which the streaks of sand found to a con-
siderable depth in the pipes were supplied.
A complete series of the diamond-field rocks has been placed in the
British Museum. Their arrangement in the country is shown by the
accompanying section from Port Nolloth to Colesberg Kopje (fig. 2).
Discussion.
Mr. Maskelyne complimented the author on the contribution
which he had made to geological science, by showing that the rock
in which the diamonds occur is confined to the pipes such as he had
described. He was able, from specimens which he had examined,
to state positively that this certainly igneous rock differed essen-
tially from the dolerites and other igneous rocks in the neighbour-
hood. He would not attempt to give it a name, whether gabbro,
euphotide, or any other designation. The materials, so far as they
could be determined in their present altered condition, were such as
would not build up any one of the known rocks. There were
garnets, and minerals resembling clinochlore, smaragdite, phlogopite,
diallage, and calcite, and apparently another mineral entirely