_Reply by the editor._--"The effect of such application of guano and plaster would be, to prevent the waste of the ammonia of the former, as every rain would decompose more or less of the plaster, separate the sulphuric acid from the lime, and the sulphuric acid when liberated, would unite with the ammonia, form a sulphate of ammonia, and hold the latter in reserve to be taken up by the roots of the plants. The presence of plaster with all _organic_ manures, either directly mixed with them, or broadcasted after they may be applied, tends to prevent the escape of their volatile parts. We prefer them together for two reasons,--_first_, because, by bringing the two into _immediate contact_, the action of the plaster is more direct; and _secondly_, because the time and expense of one sowing is thereby saved. We go for saving every way, as time and labor costs money, and we look upon economy as a virtue, which should be practised by all, and especially by husbandmen." If the plaster and guano is mixed together, 25 lbs. of the former to 100 lbs. of the latter, will be found a proper proportion, and sufficient to prevent the ammonia from making an "excursion." Unless the soil be very poor, 200 lbs. of good Peruvian guano is as much as we should recommend for wheat. In this we have the concurrence of the editor of the Farmer, and perhaps a hundred gentlemen whom we have conversed with upon this subject. All agree in the opinion, whether mixed with plaster or not, that a judicious application of guano will more certainly restore productiveness to worn out land, or add fertility to that already productive, than any other substance ever applied.