24? FANNING AND EDDINGFIELD. 
In order to see if the irregularities in the extraction per- 
centages of duplicate tests were due to varying fineness in the 
samples, screen tests were made on numbers 3, 5, 6, and 7 of lot 
1, Table XXIII, and the results are given in Table XXIV. 
TABLE XXIV.—Screen tests. Lot No. 1. 
Test 20- 40- 60- 80- 100- 150- (—) 150- 
No. Product. mesh. mesh. mesh. mesh. mesh. mesh, mesh. 
Per cent.| Per cent.| Per cent.| Per cent.| Per cent.| Per cent.| Per cent. 
Original through 60- |_---_-----_|---------_|---------- 14.10 19.30 22.10 44.40 
5 mesh s. j 0 i/Ssaces. sees esse | ee ese 15. 05 20.37 22. 85 41.80 
i) 
6 | Original through 80- 
pascoeseee|Wesceeeced BSeSezceee|usesaceaes 17.26 25.60 57.20 
7 | Original, tube-milled 
foriG OUTS eee | aaa 2 3 11.00 14. 00 11.00 54.00 
This table shows not only the fineness of the 60-mesh, 80-mesh, 
and tube-mill products, but it shows, as in 3 and 5, that the 
opposite splits of the 60-mesh product are practically identical. 
Hence the greater extraction by amalgamation (Table XXIII) 
in test 5 over that of 3 was due to variations in the free gold 
present and to losses of gold in the process of panning. 
At one time the Paracale dredge sent its quartz and table 
concentrates (after cleaning out the free gold) to a small Hunt- 
ington mill for subsequent treatment. The work of this mill 
was stated to be very unsatisfactory and the bullion recovered 
was small in consideration of the value of the ore treated. A 
great deal of the quartz is so hard as to require stamps, although 
for the treatment of the concentrates a Huntington mill would 
be better. It is very likely that if this mill had treated con- 
centrates only, it would have done far more efficient work. 
The results given in Table XXIII indicate the work which 
can be expected of a Huntington mill treating concentrates only. 
A mill using a 40-mesh screen should give results similar to 
tests 2, 8, 4, and 5 of this table, while a mill using a 60-mesh 
screen should give results similar to test 6. Judging from this, 
a Huntington mill would give an extraction of from 40 to 70 per 
cent depending on the screens, condition of the plates, etc. 
In testing ground in order to find out the values, the borings 
are placed in buckets and are later panned by hand, frequently 
using mercury to collect the gold. This method does not collect 
