the protection it receives from the action of oxidising substances other than gold, the strength of the gold solution, length of exposure to it, the rate of supply and velocity of stream, will be the size of the gold nugget.  As to the size of a pyritous mass necessary to produce in this manner a large nugget, it is by no means considerable.  A mass of common pyrites (bisulphide of iron) weighing only 12 lbs. is competent for the construction of the famous ‘Welcome Nugget,’ an Australian find having weight equal to 152 lbs. avoirdupois.  Such masses of pyrites are by no means uncommon in our drifts or the beds of our mountain streams.  Thus we find that no straining of the imagination is required to conceive of this mode of formation for the huge masses of gold found in Australia in particular, such as the Welcome Nugget, 184 lbs. 9 oz.; the Welcome Stranger, a surface nugget, 190 lbs. after smelting; the Braidwood specimen nugget, 350 lbs., two-thirds gold; besides many other large masses of almost virgin gold which have been obtained from time to time in the alluvial diggings.”

The author has made a number of experiments in the same direction, but more with the idea of demonstrating how possibly gold may in certain cases have been deposited in siliceous formations after such formations had solidified.  Some of the results were remarkable and indeed unexpected.  I found that I could produce artificial specimens of auriferous quartz from stone which had previously contained no gold whatever, also that it was not absolutely necessary that the stone so treated should contain any metallic sulphides.

The following was contributed by the author and is from the “Transactions” of the Australasian Institute of Mining Engineers for 1893:—­

“The deposition of gold.

“The question as to how gold was originally deposited in our auriferous lodes is one to which a large amount of attention has been given, both by mineralogists and practical miners, and which has been hotly argued by those who held the igneous theory and those who pronounced for the aqueous theory.  It was held by the former that as gold was not probably existent in nature in any but its metallic form, therefore it had been deposited in its siliceous matrix while in a molten state, and many ingenious arguments were adduced in support of this contention.  Of late, however, most scientific men, and indeed many purely empirical inquirers (using the word empirical in its strict sense) have come to the conclusion that though the mode in which they were composed was not always identical, all lodes, including auriferous formations, were primarily derived from mineral-impregnated waters which deposited their contents in fissures caused either by the cooling of the earth’s crust or by volcanic agency.