The term used to express the weight of the diamond and all the gems is derived from the word _Keration_, a kind of vetch, whose seeds, being generally of a uniform weight, furnished the Orientals with the means of estimating the value of precious stones. It is supposed to represent the equivalent of four Troy grains, but by actual measurement the diamond karat weighs but 3¹⁄₃ Troy grains at the present day, and it may descend even lower in the scale, unless the unit be established by law. The history of the series of diminutions by which the karat has reached its present weight is obscure, but as the term is supposed to represent four Troy grains it should equal them in reality. That it is a mere conventional weight is shown by its variance in European countries, as well as in the gem-producing countries of Asia. In making use of the term to express the weight of precious stones we would suggest that it be written karat, as more in accordance with its derivation, and that the commonly accepted word carat be used when we wish to define the alloy of certain metals, like that of gold and silver coins. Before proceeding to the subject of the valuation of diamonds, we will say a few words concerning the imitations produced by the skill of man. Many attempts at imitating the diamond have been made by experimentalists for a long time past, and much ingenuity shown by them. To those of our readers who desire to study especially these experiments we will refer them to the works of Silliman, Hare, Latour, Saix, Despretz, Dumas, Ebleman and Gaudin, Mohler, St. Clair, Deville, Gaunal, Becquerel, Joyce, Cagnard de la Tour, Mactear, Hannay, and many other well-known experimenters. Despretz’s experiments, which were based upon certain combinations of carbon, are deserving of mention. The chemists have discovered that in combining sulphur and carbon a colorless liquid is produced resembling water, and apparently containing nothing but sulphur and carbon. Therefore, Despretz reasoned, if he could get rid of the sulphur by some manner, the carbon might be crystallized. And to obtain this result, the action of the volcanic battery offered the most plausible means. With the aid of this battery the experimenter really succeeded in obtaining on a thread of platina, passed through a solution containing carbon, some small crystalline depositions, which by their form and hardness seemed to be embryonic diamonds. But here the experiment ended. Nature refused to reveal her secrets. The alchemists of the Middle Ages seeking the transformation of gold from baser metals, have been well represented by the chemists of the present century attempting to imitate the diamond. Philosophy and science have united their efforts in these fascinating experiments; but Nature still defies the most determined efforts of art in respect to the reproduction of the diamond.