308 The American Geologist. May, 1896 
It is, to our notion, by looking a1 the auriferous region of 
South Africa in its entirety that we are enabled to form true 
and rational ideas of the origin, the nature and the probable 
age of its deposits. 
A short time since descriptions and reliable geological 
studies of this country were rare. To-day there exists a 
geological society of South Africa which attacks with zeal 
the interesting problems connected with the gold deposits. 
The French engineers in the Transvaal send back interesting 
documents. The Annates de Mines has just given us an im- 
portant and substantial memoir by M. de Launay, whose con- 
clusions, however, on the origin of the auriferous deposits we 
find it somewhat difficult to accept. The Genii' Civil and other 
reviews publish in their turn interesting studies on the auri- 
ferous district of South Africa. 
M. Jules Gamier has just presented (March 6) to the 
"Societe des ingenieurs civils" a very interesting paper on 
the genesis of the gold deposits of the Transvaal. 
It appears to us that the moment is opportune for us to add 
our stone to the edifice and to contribute to the study of the 
phenomena of the deposition of gold in the southern continent. 
The facts known already seem adequate for a sketch of the 
true theory, which shall take account of all the varieties of 
deposits and all the facts observed. We believe it rational, 
and like all the other authors of theories, we entertain the 
hope of seeing it confirmed by facts, by development and by 
later studies. 
The question to be settled is, like that of the Bilbao iron 
ore, whether the gold is contemporaneous with the beds which 
contain it. 
M. de Launay answers affirmatively and concludes " there 
has been chemical precipitation of gold and of pyrite during 
the deposition of the sediments." This is equivalent to saying 
that the gold was deposited at the bottom of the sea, contem- 
poraneously with the conglomerates. And since the auriferous 
reefs exist through a thickness of many thousand meters of 
the formation we must grant, as M. de Launay adds, '"the 
constant presence or the very frequent return in the concen- 
trated waters of the sea of sulphides of iron and of gold in 
solution." 
