328 Reviews—Transraal Gold Mining. 
LV.—TransvaaL Mrynres Deparrment, Grotogican Survey. 
: ? 
Tur Gerorosy or THE Pirertms Resr Gorp Mryine Disrricr. By 
A. L. Hatt, B.A., F.G.S. 8vo; pp. 158, with 20 text-illustrations, 
33 plates, and geological map. Pretoria, 1910. Price 7s. 6d. 
N addition to the admirable reports issued annually since 1903 by 
Mr. H. Kynaston, the Director of the Geological Survey, five 
separate memoirs on special areas, accompanied by colour-printed 
geological maps, have been issued. ‘The latest of these memoirs, 
No. 5, is the one now before us. The map represents portions of the 
Lydenburg, Zoutpansberg, and Barberton Districts, an area of about 
2600 square miles. The geological formations belong mostly to the 
Transvaal System: a great series of shales, sandstones, and quartzites, 
dolomitic limestone and chert, in ascending order, divided into the 
Black Reef Series, Dolomite Series, and Pretoria (or Lydenburg) 
Series. These rocks are generally grouped as pre-Devonian, or as 
pre-Cape rocks, their age being somewhere between Devonian and — 
Archean. Correlation is not attempted in the memoir. 
As a gold-producing district that of Pilgrims Rest ranks in the 
Transvaal next after the Rand, the output for the year 1909 
amounting to a little over £400,000 in value. Mr. Hall remarks 
that the reefs occur more especially in the Dolomite and Black Reef 
Series, and mostly as ‘‘interbedded ore sheets, and thus behave 
stratigraphically exactly like the sedimentary strata in which they 
lie”. Apart from these ‘‘ flat reefs”, there are less important ‘‘ cross 
reefs”? which strike across the formations. The author, however, 
points out that ‘‘ certain features are persistent and characterize both 
varieties of reefs. These are the essentially quartzose nature of the 
reef and the constant association with metallic sulphides, notably 
pyzites and occasionally copper ores. It is therefore probable that 
the principles controlling their formation are essentially the same”. 
He concludes that ‘‘the gold was introduced in soluble form by the 
circulation of underground waters carrying silica and iron in solution, 
the gold being precipitated mainly as the result of the reduction of 
the iron to the ferrous condition ”’. 
Full particulars are given of the strata, and of the intrusive and 
contemporaneous igneous rocks in the Transvaal System. The 
geological structure is shown in a number of sections, and the 
physical features and rock-structures are represented in a series of 
excellent photographic plates. Among these is a fine view of the 
Devil’s Window, north of Belvedere, in the escarpment of the 
Drakensberg, looking towards the low country. 
V.—Cotonsay, ONE OF tHE Hesripes: irs PLANTs, THEIR LOCAL NAMES 
AND usrEs; Lraenps, Ruins, anp Puiacze-NamES; GAELIC NAMES OF 
Birps, Fisues, rrc.; Crrmare, GrorocicaL Formation, erc. By 
Mourvocu McNertr. pp. vii, 216. Edinburgh: David Douglas, 
1910. Price 2s. 6d. net. | 
OLONSAY with its adjunct Oransay, for they are connected for 
several hours during low water, is about 12 miles in length and 
3 in breadth. As represented on Sir Archibald Geikie’s map of 
