Amalgam (chemistry) gold") would not be extractable from ore using hydro-mechanical methods. Large amounts of mercury were used in "placer mining", where deposits composed largely of decomposed granite slurry were separated in long runs of "riffle boxes", with mercury dumped in at the head of the run. The amalgam formed is a heavy solid mass of dull gray color. (The use of mercury in 19th century placer mining in California, now prohibited, has caused extensive pollution problems in riverine and estuarine environments, ongoing to this day.) Sometimes substantial slugs of amalgam are found in downstream river and creek bottoms by amateur wet-suited
What Is History? to suit their facts, and takes part in a dialogue between past and present. Summing up his argument, Carr puts forward his own answer to the question of "what is history?", remarking that "it is a continuous process of interaction between the historian and his facts, an unending dialogue between the past and the present." it is precisely for matters of this kind that the historian is entitled to rely on what have been called the auxiliary sciences of history In his second chapter, Carr focuses on the influence that society plays on forming the approach of the historian and