No doubt on that point, provided it is good manure. Barn-yard manure, whether rich or poor, contains all the elements of plant-food, but there is a great difference between rich and poor manure. The rich manure contains twice or three times as much nitrogen and phosphoric acid as ordinary or poor manure. And this is the reason why artificial manures are valuable in proportion to the nitrogen and phosphoric acid that they contain in an available condition. When we use two or three hundred pounds per acre of a good artificial manure we in effect, directly or indirectly, convert poor manure into rich manure. There is manure in our soil, but it is poor. There is manure in our barn-yard, but it is poor also. Nitrogen and phosphoric acid will make these manures rich. This is the reason why a few pounds of a good artificial manure will produce as great an effect as tons of common manure. Depend upon it, the coming farmer will avail himself of the discoveries of science, and will use more artificial fertilizers. But whether we use artificial fertilizers or farm-yard manure, we shall not get the full effect of the manures unless we adopt a judicious rotation of crops. When we sow wheat after wheat, or barley after barley, or oats after oats, we certainly do not get the full effect of the manures used. Mr. Lawes’ experiments afford conclusive evidence on this point. You will recollect that in 1846, one of the plots of wheat (10_b_), which had received a liberal dressing of salts of ammonia the year previous, was left without manure, and the yield of wheat on this plot was no greater than on the plot which was continuously unmanured. In other words, _the ammonia which was left in the soil from the previous year, had no effect on the wheat_. The following table shows the amount of nitrogen furnished by the manure, and the amount recovered in the crop, when wheat is grown after wheat for a series of years, and also when barley is grown after barley, and oats after oats. Table Showing the Amount of Nitrogen Recovered, and Not Recovered, in Increase of Produce, for 100 Supplied in Manure.