Rough diamonds, fit for cutting, are sold at 41 13s. 4d., to 42 the carat. A carat is rather more than three grains, and 156 carats equal to one ounce Troy. But if the stones ' are above one carat, the square of the weight is multiplied by the price of a single carat; so that, for example, a rough stone of three carats costs 3x3x 2 or 18. It is similar with : cut diamonds, and in 1850 the purest briliants of one carat brought more than 8, a brilliant of two carats 2x2x 8, or 32. When sjojjes aje,over ejght or te" carats, however, this is altered, so that they are valued still more highly. Diamonds of a quarter ot an ounce weight are extraordinarily costly, but still larger are met with ; and one of the largest known is that of the rajah of Mattun, in Borneo, which weighs nearly two ounces and a hall ; that of the Sultan of Turkey weighs two ounces ; one in the Russian sceptre more than an ounce and a quarter.— The greatest diameter of the last is one inch, the thickness ten lines. The Empress Catherine II. purchased it in the year 1772, from Amsterdam, and for it was paid 475,000, and an annuity of 4650. Diamonds weighing an ounce exist also in the French and Austrian regalia. One of the most perfect is the French, known as the Pitt or Regent diamond. It was bought for Louis XV., from an Englishman named Pitt, for the sum of 4135,000 sterling, but has been valued at half a million. One of the stones most renowned in the East, is the Koh-i-noor,or Mountain of Light, now in possession ot the Queen of England. It came from Golconda to Persia, and while uncut weighed more than five ounces, but now, polished, only about two ounces. It is valued at more than 42,000,000 sterling. If we look only to the common mode of estimating the value, a perfect brilliant weighing half a pound, would be worth 420,000,000. Some have stated that such a diamond exists among the royal treasures of Portugal as large as a hen's egg; according to others this is only a topaz.