ORIGIN OF GOLD NUGGETS. 325 
Experiment 22, with rust.—A mixture of black and brown 
oxides from old sheet iron. The gold foil became very dull and 
dirty looking. Increased -0011 g. in fifty-nine days. On dissolv- 
ing the residue in hydrochloric acid, only dark coloured spongy 
gold was left. 
Experiment 23, with yellow copper pyrites.—After fifteen days 
the gold plate was dull from deposited gold. Increase in weight, 
0059 g. in fifty-nine days. 
Experiment 24, with copper pyrites.—Reduced several charges 
of the gold solution. The foil became deeply stained, and acquired 
a rough appearance and feel, of the usual brown colour; under 
the microscope it was seen to be much mammillated; and increased 
°0185 g. in weight in fifty-nine days. A large amount of gold 
was also thrown down on the pyrites, which under the microscope 
was seen to havea matted vermiform appearance; a certain amount 
of loose powdery gold was also precipitated. 
Experiment 25, with copper pyrites, Walleroo,S.A.—The deposit 
of gold was almost black but mixed with it were a few very bright 
microscopic hexagonal plates of gold. The deposit of gold on the 
plate was very rough and almost black in places, and it had 
increased in weight 0666 g. 
Haperiment 26, with redruthite (copper subsulphide).—The gold 
was deposited on the sulphide as a black powder, with a little dull 
yellow in parts. The gold plate became of a dull brown colour 
near where it had been in contact with the mineral, the upper 
part was merely stained. Increase = ‘0836 g. 
Experiment 27, with silver sulphide (argentite).— No change for 
some time, but between June 28, and November 30, it reduced 
five ounces of the gold solution and became coated with gold. 
Some of the gold was crystallised in microscopic imperfect hexa- 
gonal scales. The gold plate increased :0083 .g. in one hundred 
and fifty-five days. 
Experiment 28, with fused artificial silver sulphide.—The gold 
deposited upon it was vermiform, and a thin coating of dead 
