There is a certain rule for estimating the price of a diamond, and singular to say it is the old Indian rule by which Tavernier was guided in his purchases, and which modern commerce has been content to let stand. The current market price of a good cut diamond, one carat in weight being ascertained, the square of the weight of the diamond to be valued is multiplied by that figure. The present selling price in London of a clear and faultless cut diamond one carat in weight is one hundred dollars, one of three carats therefore would be worth 3×3×100=$900. Were our advice asked with regard to the purchase of these valuable pebbles whose history has so long occupied our attention, we should refer our interlocutor to that Chinese philosopher who on being asked why he kept bowing and saying, "Thank you, thank you," to the gem-bedecked mandarin, replied: "I am thanking him for buying all those diamonds and undertaking the trouble and anxiety of keeping them safe that I, undisturbed, may look at them and admire them at my leisure." XI. A FAMOUS NECKLACE. That the human neck is a suitable pillar to hang ornaments upon is so obvious a fact that it must have presented itself to the most rudimentary savage; and that it did thus occur to the early human mind we have abundant evidence. The prehistoric graves of Europe give up a greater quantity of necklaces to the antiquarian searcher than almost any other article, with the exception of implements of war. These necklaces are differently composed of beads of glass and of amber, colored pebbles and small gold plaques, while the white teeth of various animals and sea-shells seem to have been as general favorites with the prehistoric as with the contemporary savage. It is not our intention to give an account of the many types of necklaces which have found favor in the eyes of humanity. To do so would be quite beyond the scope of these stories. We propose on the contrary to select but one--one especially notable amid the necklaces of the past. We may mention that the first diamond necklace ever known in Europe was one composed of rough stones which was given by Charles VII. of France to Agnes Sorel. The fair lady's soft neck was so irritated by the sharp corners of the necklace that she said it was her pillory (_carcan_), hence the term _carcanet_ which means a diamond necklace. The term fell into disuse about the time of the Revolution, and the proper name in France for a string of diamonds at that period was _rivière_. Nowadays they have restored the _carcanet_ and kept the _rivière_ as well, both terms being in common use. Of all the necklaces in all countries and all times, incomparably the most famous was that one with which Marie Antoinette's name was so unhappily associated. This trinket is still disputed about even in our own times. It has a literature of its own and it is emphatically The Necklace of History. We will endeavor to make clear its singular career and ultimate fate.