Some consider those metals most precious which, like gold and silver, have earned that reputation by acting in the capacity of representatives of wealth, as the current coins of civilized nations. To some men these have been esteemed more precious than health, or even than life itself; others, calculating on the grounds of utility, have considered iron and copper, so universally applicable to the wants of civilized life, such mighty agents in the cause of civilization, as the most precious of metals; and these may be right in their calculations, for although we might manage to get on without the former, we can hardly imagine for ourselves the condition occasioned by the loss of the latter. There are yet a few to whom it would seem, however strange the fact may appear, that two metals are the most precious which the rest of the world have no idea of considering as of but a very low rate of value, and without which they can readily conceive of the world moving on without any very great sense of their loss. These two are Arsenic and Mercury. The very names are almost sufficient to send a shudder of horror through us as we write or repeat them; and to elect them into the highest place in our affections is the last act we should, in a state of sanity, deem ourselves likely to perform. The one suggests images of Aqua Tophana and the Middle Ages, and our teeth loosen in our gums with unpleasant reminiscences of black draught and blue pill as associated with the other. For one we can think of no better employment than the extirpation of rats, or the preservation of mummies; and for the other no more exalted an occupation than to coat the backs of our mirrors, or inform us of the conditions of the atmosphere. That any one could indulge in them as luxuries, or, by their habitual use, elevate them to a companionship with tobacco and opium, with haschish and coca, would appear to be a gross libel upon the “Seven Sisters of Sleep,” and a satire upon the cherished companions of millions of the human race. Medical men, foremost amongst whom is Dr. Christison, consider that these minerals cannot be indulged in without exercising a deleterious effect upon the system. The cumulative action of mineral poisons is a great point of difference between them and those of vegetable origin, for although the same eminent physician is of opinion that tobacco may be indulged in without injury, he does not believe such a possibility to exist with regard to mercury and arsenic.[32]