The successful treatment of battery slimes by cyanide has until recently been a very vexed question in all mining communities. Several methods have been tried with a view to overcoming the difficulties. These, however, have been abandoned owing to the poor extraction and the high cost of treatment. The difficulty has been got over with highly satisfactory results by agitation. My remarks in this paper will be of a practical nature, dispensing with all the chemistry of cyanidation. My only object being to give the members of this Institute my experience in the treatment of the water which overflows from the cyanide vats and carries off the slimes in suspension. I propose to deal with this subject under three different headings. 1. The collection of the slimes. 2. Their treatment by cyanide. 3. The precipitation of the gold by charcoal. I will also touch lightly on the merits of the two precipitants, charcoal and zinc. I take it for granted that you all understand the treatment of quartz in a battery house, the various methods adopted for catching free gold, also the concentrating of tailings to catch the pyrites. It is after all these known methods have been adopted that I want to show the necessity of a special treatment of the water which carries off the slimes in suspension, and which, if adopted, will yield a handsome revenue to any company that will take the trouble to adopt it.