8 PBOCEBDINGS OP THE GEOLOGICAL SOCIETY. [NoV. 8, 



and therefore exhibit more perfectly the proportion of the several 

 kinds. Garnets are unequally scattered throughout the mass. Frag- 

 ments of fossil wood are frequently met with. A great mauy of 

 the pebbles are found in a fragmentary condition, owing, probably, 

 to the action of the large boulders with which they are associated. 

 Shafts have been sunk into these deposits to a depth of more than 

 30 feet. 



In some places immediately below this gravel there is a thin . 

 layer (a few inches thick) of a very fine tough yellowish clay, almost 

 like an ochre ; and below this are the ancient rocks that form the 

 floor of the valley of the Yaal. 



This boulder-gravel extends for a considerable distance, almost 

 parallel with the course of the river, forming a terrace-like ridge, 

 which finally slopes down towards the bank. This is the deposit 

 in which a large number of diamonds have been found ; the largest 

 have all been within 2 feet of the surface. 



The same gravel is found on the opposite side of the river at 

 Klip Drift, but in much smaller quantity. The component peb- 

 bles are shown by those sent. See Nos. 7, 8, 9, Appendix. 



Fragments of fossil wood are more plentiful here and at He- 

 bron than in any other portion of the diamond-deposits yet 

 examined. 



The upper portion of the gravel, which diminishes in some places 

 to a thickness of 5 feet, and in others even to a single foot, is 

 placed upon a thin laminated layer, from 6 to 8 inches thick, 

 spread over the floor of many of the " claims," adapting itself to 

 the inequalities of the deposit on which it lies. On breaking 

 through it, a yellowish and rather ochreous clay is found ; and, 

 although shafts of 10 feet have been sunk into it, its thickness is . 

 not at present known. These deposits evidently rest upon the 

 rocks before mentioned. 



Islands in the river here are of frequent occurrence : most of 

 them are composed of gravel, which is apparently of a far more 

 recent origin than that of the Kopjes and the terrace -like accumula- 

 tions of Gong-Gong and Pniel. Some of them have trees growing 

 them, as the island near the last-mentioned place. Several of 

 these islands have been examined for diamonds, but with little 

 success. The rapids, which also are very numerous, seem to be 

 caused by felspathic dykes crossing the bed of the river. 



Section III. At a distance of about twenty-four or twenty-five 

 miles further up the river are the Hebron diggings. I have been 

 able to obtain a more complete section of this locality than of the 

 others. In this there is an evident sequence in the gravels ; and it 

 throws considerable light upon the true position of those we have 

 been considering. 



Hebron and Diamondia. — This section (fig. 2), commencing atDia- 

 mondia, passes through the " lagoon " in the ancient river-bed (see 

 Map), then shows the lower gravel, thence crosses the river to the 

 upper kopjes on the Hebron side. 



The uppermost deposits are those numbered Nos. 5, 6, and 7- 



