We suppose these facts and reasons to establish our theory, that the principal benefit of manures, and of mixing different soils, is in the control they give over the moisture and the atmosphere. Hence the greatly increased crop of clover from the application of three quarters of a bushel of plaster to an acre. The increased weight of clover on five square rods, would outweigh the plaster applied, and still that plaster remains, in almost its full weight, on the soil. This principle explains the benefit of mulching trees, plants, or vegetables. This is the best means of preserving trees, the first year after transplanting, and of securing a great growth, of any kind of shrubs or plants. This may be done with common straw or leaves. Now wherein is their utility? Not in the nourishment they afford the plants, but in the fact that mulching so covers the surface as to prevent rapid evaporation. In such cases, it is the more abundant moisture that secures the greater growth. Hence the first study of a soil culturist should be to ascertain how he shall so mix and manage the materials at his command, as to cause them to retain moisture for the longest time, without leaving water to stand about the roots of his plants. On this depends the whole importance of deep plowing and ditching. On this theory we may also account for the fact that certain plants prefer a certain kind of manure to all others. It is that those plants act in a certain manner on the soil requiring a specific action of manure to enable it to appropriate moisture and tax the atmosphere for their growth. This theory explains why too much manure is bad. Not because we give too much food to plants, but because excess of manure dries up the land. But whatever theory we adopt, we all agree in the utility of fertilizers. And the experience of practical farmers is of more value in aiding us to reach right conclusions, than all chemical essays on the subject that have ever been written. MARL. This is one of the best distributed and most universal fertilizers. Marl proper contains nearly equal proportions of clay and lime. Sand-marl is spoken of, in which sand and lime are the main ingredients. Clay-marls are to be applied to sandy and gravelly soils, and sand-marls to clayey soils. Shell-marls are very valuable, and seldom contain clay. Marls may easily be known, even by those not at all acquainted with chemistry. Apply any mineral acid, or even very strong vinegar, and if it be a marl, an effervescence will at once be observed: this effect is produced by acid upon lime. MARJORUM. There are two varieties in cultivation--the _sweet_, an annual herb; and the _winter_, a hardy perennial. They are grown and used as summer savory--used green, or dried for winter. They give a sweet, aromatic flavor to soups, stews, and dressings. The cultivation is, in all respects, like other garden-herbs of the kind, whether for medicinal or culinary purposes. MELONS.