From these results the value of the commercial article has been attempted to be ascertained. As it contains 80 per cent or thereby of fine meal and 20 per cent of coarse, its activity may be stated to be 50, or half as active as super. Thus 2 cwt. of basic slag is equal to 1 cwt. of super. This only refers to the first year's effect. Professor Wagner has made further experiments as to the after-effects of the different manures, with the result that he has found that the after-effects of the basic slag are even _better_ than those of the "super." This stands to reason, for if twice as much phosphoric acid be added in the form of basic slag as is added in the form of "super," and the effect of the first year is similar--that is, the same quantity of phosphoric acid is assimilated by the plant from the soil in both cases--there is naturally more phosphoric acid left behind in the soil manured with basic slag than in that manured with superphosphate of lime. For example, if 100 lb. of super has the same effect in the first year as 200 lb. of basic slag, and it is found that only 60 lb. of the super and the basic slag have been assimilated the first year by the plant, it is only natural to conclude that the remaining 140 lb. of the basic slag will have a better after-effect than the remaining 40 lb. of super. This has been actually proved to have been the case in Professor's Wagner's experiments. The following are the results of some experiments which Professor Wagner has carried out on the after-effects of different manures:-- Out of 100 parts of phosphoric acid, there was removed by the first year's crop-- Super 63 Peruvian guano 22 Bone-meal 7 Coprolites 6 Thomas-meal-- No. 1 fineness 39 No. 2 " 43 No. 3 " 15 Out of 100 parts of phosphoric acid left by the first crop, there was removed by the three succeeding crops-- Super 30 Peruvian guano 9 Bone-meal 13 Coprolites 6 Thomas-meal-- No. 1 fineness 14 No. 2 " 29 No. 3 " 24 Numerous other experiments have been carried out by various experimenters in different parts of Germany which it is unnecessary to cite here. None, however, are so complete as those of Professor Wagner. _Results of other Experiments._