192 DISCOVERIES OF THE FRENCH. 
posed of gold, which occurs in the form of small 
lumps, grains, and spangles, mechanically united 
with earth, emery, and grains of iron ore. At the 
first four feet from the surface, there occurs a fat 
argillaceous earth, mixed with small particles of iron 
ore and emery, and from which the gold is ex- 
tracted by agitation in the form of dust. In dig- 
ging deeper, the gold is found in larger grains, with 
lumps of emery and lapis lazuli, which are entirely 
covered with this precious metal. At the depth 
of twenty feet, it begins to appear in small lumps, 
of from two to ten grains. At forty feet, the 
greatest depth yet reached, still larger pieces are 
found, sometimes to the amount of fifteen grains ; 
and there is every reason to believe, that, on de- 
scending lower, the metal would be found in still 
greater abundance. All the rivulets, besides, 
which pass through the plain of Natakon, roll 
golden sands ; and the Colez, called by the Por- 
tuguese Rio d'Oro, which descends from the moun- 
tains of Tabaoura to the Senegal, bears in its bed a 
considerable proportion of this precious metal. 
About 40 miles to the north of the mine of Na- 
takon, in descending the course of the Rio d'Oro, 
is the mine of Semayla. It is connected with the 
western branch of the same chain of mountains, 
and is situated in a hillock of a similar aspect, 
though not so entirely insulated. This hillock is 
not above 200 feet in height, but it has a circum- 
