The process of extracting gold from ores by absorption of the precious metal in chlorine gas, from which it is reduced to a metallic state, is not a very new discovery.  It was first introduced by Plattner many years ago, and at that time promised to revolutionize the processes for gold extraction.  By degrees it was found that only a very clever chemist could work this process with practically perfect results, for many reasons.  Lime and magnesia might be contained in the quartz, and would be attacked by the chlorine.  These consume the reagents without producing any results, earthy particles would settle and surround the small gold and prevent chlorination, then lead and zinc or other metals in combination with the gold would also be absorbed by the chlorine; or, again, from some locally chemical peculiarity in the water or the ore, gold held in solution by the water might be again precipitated in the tailings before filtration was complete, and thus be lost.  Henderson, Clark, De Lacy, Mears, and Deacon, all introduced improvements, or what were claimed to be improvements, on Plattner, but these chiefly failed because they did not cover every particular variety of case which gold extraction presented.  Therefore, where delicate chemical operations were necessary for success, practice generally failed from want of knowledge on the part of the operator, and many times extensive plants have been pronounced useless from this cause alone.  Hence it is not to be wondered that processes requiring such care and uncommon knowledge are not greatly in favor.

Mr. Claude Vautin, a gentleman possessed of much practical experience of gold mining and extraction in Queensland, together with Mr. J. Cosmo Newbery, analytical chemist to the government of Victoria, have developed a process which they claim to combine all the advantages of the foregoing methods, and by the addition of certain improvements in the machinery and mode of treatment to overcome the difficulties which have hitherto prevented the general adoption of the chlorination process.

By reference to the illustrations of the plant below, the system by which the ore is treated can be readily understood.  The materials for treatment—­crushed and roasted ore, or tailings, as the case may be—­are put into the hopper above the revolving barrel, or chlorinator.  This latter is made of iron, lined with wood and lead, and sufficiently strong to bear a pressure of 100 lb. to the square inch, its capacity being about 30 cwt of ore.  The charge falls from the hopper into the chlorinator.  Water and chlorine-producing chemicals are added—­generally sulphuric acid and chloride of lime—­the manhole cover is replaced and screwed down so as to be gas tight.  On the opposite side of the barrel there is a valve connected with an air pump, through which air to about the pressure of four atmospheres is pumped in, to liquefy the chlorine gas that is generated, after which the valve is screwed down.  The barrel is