Gold Mining Notes. 51 
bought. The mode of using the needles is as follows : 
The metal to be tested is rubbed on the touch-stone 
and leaves a metallic streak, which is compared with the 
needles placed in succession beside it, until one is found 
which appears to the eye the same in colour. A streak 
is then made with this needle near the streak to be 
tested, and both are compared under a common lens. 
If they are exa6tly alike, the test streak is supposed to 
be of the same fineness as the needle ; if not, other needles 
are tried and the result is confirmed by touching the two 
streaks with nitric acid on a glass rod. 
Greater accuracy is of course obtained by assay, full 
directions for which are contained in the report, which 
it is not deemed necessary to transfer to this paper. For 
all practical purposes, the test needles will give suffi- 
ciently exact results, and having ascertained the amount 
of gold in a 4 lb. washed sample, and the fineness by 
the process just described, the table given by Mr. 
ATTWOOD and transcribed on p. 49, will shew the 
amount of free gold per ton of 2,000 pounds avoirdupois. 
In the Fourth Annual Report, that for 1884, there are 
full directions for conducting an assay of bullion, but 
space does not allow of their being transferred to these 
pages ; besides which, the operation is a delicate one, 
requiring practice and experience, and therefore more 
properly left to professional persons. 
The amalgam is treated in the following manner called 
retorting, to drive off the mercury employed, and obtain a 
residuum of gold. The retort used for small operations 
is a bowl-shaped vessel of cast iron — its top edge 
smoothed so as to be in complete contact with the planed 
edge of the cover so that the two form a perfect joint. 
G 2 
