IN dealing, with this subject the writer does not propose to enlarge upon the obvious advantages of any great up-to-date plant, of which there are so many on this field, nor upon the well-known simple principles of cyaniding fresh or non-refractory tailings, so much as to describe the methods which have been found best in treating a particular class of refractory tailings, pointing out the difficulties to be overcome and serious errors that have been corrected.