St. Croix is an island, about eighteen miles long, situated in latitude 17 deg. 45' north, longitude--west of Greenwich. It is almost exclusively devoted to the cultivation of sugar-cane, and the manufacture of sugar molasses, and rum. In a good season it produces from fifty to sixty thousand hogsheads of muscovado sugar of the best quality. It is generally calculated that the molasses and rum will pay all the contingent expenses of the estates; leaving the sugar for clear income, which at seventy-five dollars the hogshead, for which it is generally sold there, in a good season, amounts to three millions seven hundred and fifty thousand dollars. This great revenue is produced by the careful cultivation of almost every inch of the soil, the estates generally consisting of but one hundred and fifty to three hundred acres each; and nearly one hundred negroes being employed upon each one hundred and fifty acres. The soil is dry and sweet, producing the best cane, and consequently the best sugar known. I had heard much of filthiness in the manufacture of sugar and molasses, but the first view of a St. Croix sugar works contradicted it. The kettles, the vats in which the sugar is cooled, the hogsheads in which it is drained, and even the molasses vats under them, are so perfectly neat and clean, that no one who has seen them can feel any squeamishness in eating St. Croix sugar, or molasses either. To look at a vat-full, a foot deep, just chrystalizing over the surface, and perfectly transparent to the bottom, would satisfy the most scrupulous upon this point. There is about twenty-five thousand black, and three thousand white population. Of course, it is seldom a white man is seen in riding through the island.