Hydrogen, although a gas, is recognized by chemists as a metal, and when combined with any solid metal--as in the case known to electricians as the polarization of a negative element,--the compound may correctly be termed an alloy; while any compound of hydrogen with the fluid metal mercury may with equal correctness be termed an amalgam of hydrogen, or "hydrogen amalgam." The efforts of many chemists and mining engineers have for many years been devoted to a search for some effective and economical means for preventing the "sickening" of mercury and its consequent "flouring" and loss. Some sixteen or more years ago, Professor Crookes, F.R.S., discovered and, after a series of experiments, patented the use of an amalgam of the metal sodium for this purpose. He made the amalgam in a concentrated form, and it was added in various proportions to the mercury used for gold amalgamation. Water becoming present, it will readily be understood that the sodium, in being converted into the hydrate (KHO) of that metal, caused a rapid evolution of hydrogen. The hydrogen thus evolved was the excess over a certain proportion which enters into combination with the mercury. While the mercury retained the charge of hydrogen, the "quickness" of the fluid metal was preserved; but upon the loss of the hydrogen the "quickness" ceased, and the mercury was acted upon by the injurious components contained in the ore. Since the introduction of the sodium amalgam, many attempts have been made, more especially in America, to overcome the tendency of mercury to "sicken" and lose its "quickness." The greater number of these efforts have been made by the use of electricity as the active agent in attaining this end; but such efforts have been generally of a crude and unscientific character. Latterly Mr. Barker, of the Electro-amalgamator Company, Limited, has introduced a system--already detailed in these pages--by which the mercury is "quickened." In his method the running water passing over the tables, or other apparatus of a similar character, is used as the electrolyte. In this arrangement, the mercury being the cathode, plates or wires of copper constituting anodes are brought into contact with the water passing over the mercury in each "riffle." Both the cathode and the anodes are, of course, maintained in contact with the poles of a suitable source of electrical supply. The current then passes from the copper anode through the running water to the mercury cathode, and so on to the negative pole of the electro-motor. As a consequence of this arrangement, hydrogen is evolved from the water, and has the effect of reducing any oxide or other detrimental compound of the metal; in other words, it "quickens" and prevents "sickening" of the fluid metal, and consequent "flouring" and loss. While the hydrogen is evolved at the cathode, oxygen enters into combination with the copper constituting the anodes. This to some extent impairs the conductivity of the circuit.