We may take another view of the subject solely with the artistic eye, and find much for enjoyment and contemplation. In the art of ancient times the precious stones played an important part, and by means of the engraved gems we are enabled to form an idea of the wonderful skill of the artists of those periods. By means of these engraved stones the portraits of many of the illustrious characters of antiquity have been preserved, and also representations of some of the masterpieces of sculpture, which have since been destroyed by time or the hand of barbarism. If the reader, exercising a little credulity and patience, will kindly follow me through the observations of many years here condensed and recorded, he may in a slight degree partake of some of the enthusiasm and interest of the author. But, before we proceed very far on the pleasant and seductive journey, let us understand each other, and, above all, allow the author to confess that his knowledge of the subject is decidedly imperfect, and perhaps somewhat visionary at times. We will consider first the diamond, not because we regard it the foremost in interest among minerals, but because it is to-day reckoned commercially, as it was in the time of the Latin philosopher, Pliny, nearly two thousand years ago, “Maximum in rebus humanis,”--“The most costly of human possessions.” But we must, however, slightly modify the remark, and now apply it to the rare colored varieties of the gem, since commerce and refined taste rank the red sapphire far above the colorless diamond in value, and sometimes even the emerald and rare blue sapphires exceed it in price. It is interesting, and at times amusing, to read the views of the ancient gem-writers, and even those of mediæval times, relating to this remarkable mineral, and compare them with the accepted opinions of the present day. The ancients were completely ignorant of the nature of the stone, and called it “adamas,” or the invincible, from the mistaken idea that it could resist all external violence, and was also perfectly indestructible. Modern science, however, has disclosed the fact that the gem is not only quite delicate in its structure, but that it is also utterly perishable in its nature. The revelations of chemistry have clearly demonstrated that the glittering stone, known as the diamond, is simply crystallized carbon, and one of the allotropic forms of that protean element which, by the aid of some mysterious agency, can deposit its substance in the shape of a sooty blackness, as in the coal, or in the transparent crystal of diamond, which may be regarded as the very emblem of light. Furthermore, the gem is not only the concentrated embodiment of human valuation, but it is also the standard of hardness among all mineral substances; and yet, strange to say, plumbago, which apparently is of the same composition, is exactly the reverse, and quite as soft as talc.