Page:Archaeological Journal, Volume 9.djvu/183

 ON THE ASSAY MARKS OX GOLD AND SILVER PLATE. 1:20 We now proceed to consider the origin and liistory of our English marks. The first mention we find of a mark is in the year 1300, when it seems that frauds were committed to such an extent that the interference of the legislature became necessary, for in that year, 28th of Edward I., it was ordained by statute that no goldsmith should make any article of gold or silver unless it be of good and true alloy, that is, gold of the " touch of Paris," and silver of the alloy of the sterling coin ; that all articles should be assayed by the wardens of the craft, and marked with the leopard's head; that the wardens should go from shop to shop among the goldsmiths to assay if the gold be of the aforesaid " touch," and that everything which they should find of lower standard should be forfeit to the Kins; : that no false stones should be set in gold, and no real stones in base metal. We here see the " wardens of the craft " called into operation to assay suspected articles and to mark those of the true standard with the "leopard's head." This is the earliest mention I find of an assay. The process of the assay in contradistinction to the " touch " is as follows : — for gold, a portion of metal scraped off the article to be examined, after being accurately weighed, is digested in nitric acid, which dissolves the copper, silver, &c., leaving the gold in the form of a black jDOwder, which may be fused into a button of the pure metal, and the difference in weight will show the quantity of alloy. The silver is thrown down from the solution by common salt, and the copper is precipitated by iron. For silver, the process is by the cupel : a certain portion, usually about ten or twenty grains is scraped off the article, some being taken from each separate part ; it is accurately weighed, and Avrapped in a piece of pure lead foil of proportionate weight : this is placed in a small, shallow, porous crucible, made of bone ashes, called a cupel, and exposed to a bright red heat. The metals melt ; the lead and alloying metals become oxydiscd, and are absorbed by the cupel, leaving a button of pure silver ; the difference in weight between the remaining button and the original weight shows the amount of alloy. Of this process a minutely-detailed account is given in a small book published in 1675, called "A Touchstone for Gold and Silver Wares ;" and the process is now carried on