Gypsum is a chemical compound of Sulphur and Lime--so much is agreed; and the theory of chemists has been that; as the winds pass over a surface sown with it, the Ammonia which has been exhaled by a thousand barn-yards, bogs, &c., having a stronger affinity for Sulphur than Lime has, dissolves the Gypsum, combines with the Sulphur, forming a Sulphate of Ammonia, and leaves the Lime to get on as it may. I accept this theory, having no reason to distrust it; and, knowing that Sulphate of Ammonia is a powerful stimulant of vegetable growth (as any one may be assured by buying a little of it from some druggist and making the necessary application), I can readily see how the desired result _might_ in this way be produced. For our purpose, however, let it suffice that _it is_ produced, of which almost any one may be convinced by sowing with Gypsum and passing by alternate strips or belts of the same clover field. I suspect that not many fertilizers repay their cost out of the first crop; but I account Gypsum one of them; and I submit that no farmer can afford not to try it. That its good effect is diminished by many and frequent applications, is highly probable; but there is no hill or slope to which Gypsum has never yet been applied which ought not to make its acquaintance this very year. I am confident that there are pastures which might be made to increase their yield of Grass one-third by a moderate dressing of it. I have heard Andrew B. Dickinson, late of Steuben County, and one of the best unscientific, unlearned farmers ever produced by our State, maintain that he can not only enrich his own farm but impoverish his neighbors' by the free use of Gypsum on his woodless hills. The chemist's explanation of this effect is above indicated. The plastered land attracts and absorbs not only its own fair proportion of the breeze-borne Ammonia, but much that, if the equilibrium had not been disturbed by such application, would have been deposited on the adjacent hills. As Mr. D. makes not the smallest pretensions to science, the coincidence between his dictum and the chemist's theory is noteworthy.