The Extraction of Gold. 15 
now being conducted by Mr. Newbery are known. In con- 
clusion, I beg to acknowledge my indebtedness for some 
points in the foregoing to a Report on the Minerals of Vic- 
toria, just completed, by Mr. G. F. Ulrich, of the Geological 
Survey. 
Art. II].—On the Extraction of Gold. By Mr. H. A. 
THOMPSON. 
(Read 11th September, 1866.) 
The paper I have the honour to lay before the Royal 
Society has been compiled from my notes of experiments 
extending over the last six or seven years, and entered upon 
with a view of diminishing the heavy loss of gold now 
sustained in reducing quartz. The greater portion of these 
experiments were carried out at the works of the Port 
Phillip Company at Clunes by the officers of the company, 
or in conjunction with them, and are the more important as 
on that large establishment there is every facility for con- 
ducting the trials upon a working scale, while an assay office 
attached to the works allows of every step being tested 
with the accuracy which alone can make the results obtained 
reliable. It has long been known that a greater loss occurs 
in the treating of gold ores than is the case with any other 
metal ; and although this subject has attracted the notice of 
scientific and practical men for many years, the advance 
hitherto made has hardly been commensurate with the atten- 
tion bestowed upon it. 
In the old gold mining works of Europe and South 
America the loss runs from twenty-five per cent. of the total 
contents of the quartz upwards, notwithstanding the accu- 
mulated experience of several generations of miners; and in 
California Professor Silliman reports that his examination of 
tailings from the different works in the Grass Valley, showed 
a loss of eighty dollars (say four ounces) of gold per ton, and 
he adds, “on the authority of one of the most cautious and 
experienced metallurgists of California, that the saving in a 
large number of cases was barely thirty per cent. of the 
gross contents of the ore, as determined by his own careful 
assays both of the ore and the waste.” 
In this colony assays of tailings from many cleerennt gold- 
fields have led me to the conclusion, that the average loss 
sustained in crushing is not less than thirty-five per cent. of 
