An agricultural essayist in Maine has recently put forth a canon which, if well grounded, is of great value to farmers. He asserts that the growth of acid plants like Sorrel, Dock, etc., in a field, results from sourness in the soil, and that, where this exists, Lime--that is, the ordinary Carbonate of Lime--is urgently required; whereas the application of Plaster or Gypsum (Sulphate of Lime) to that field must be useless and wasteful. If such be the truth, a knowledge of it would be worth millions of dollars to our farmers. But I lack the scientific attainment needed to qualify me for passing judgment thereon. There is great diversity of opinion among farmers with regard to the value of Swamp Muck. One has applied it to his land to good purpose; so he holds Muck, if convenient, the cheapest and best fertilizer a farmer can add to his ordinary barn-yard manure; another has applied cords upon cords of Muck, and says he has derived therefrom no benefit whatever. Now, this contrariety of conclusion may result from imperfect judgment on one side or the other, or from the condition precedent of the diverse soils: one of them requiring what Muck could supply, while the other required something very different from that; or it may be accounted for by the fact that the Muck applied in one case was of superior quality, and in the other good for nothing. Where Muck is composed almost wholly of the leaves of forest-trees which, through thousands of years, have been blown into a bog, or shallow pond, and there been gradually transformed into a fine, black dust or earth, I do not see how it can possibly be applied to an upland, especially a sandy or gravelly soil, without conducing to the subsequent production of bounteous crops. True, it may be sour when first drawn from the stagnant pool or bog in which it has lain so long, and may need to be mixed with Lime, or Salt, or Ashes, and subjected to the action of sun and frost, to ripen and sweeten it. But it seems to me impossible that such Muck should be applied to almost any reasonably dry land, without improving its consistency and increasing its fertility. But all Muck is not the product of decayed forest-leaves; and that which was formed of coarse, rank weeds and brakes, of rotten wood and flags, or skunk cabbage, may be of very inferior quality, so as hardly to repay the cost of digging and applying it. Science will yet enable us to fix, at least approximately, the value of each deposit of Muck, and so give a preference to the best.