TRANSACTIONS OF SECTION B. 315 



matter in the water should have increased owir.g simply to this increase in quantity 

 is not at first sight very clear. 



It may be possible that the largely increased number, area and length of air- 

 ways has a tendency to expose the water for a longer time to oxidising influences, 

 and thus add to the percentage of sulphates, and this increased facility for oxidation 

 no doubt also induces more rapid solution of the strata as the water slowly permeates 

 through it. 



The author hopes these few imperfect observations may not prove altogether 

 uninteresting to those who take pleasure in the study of mineral waters. 



1UESDAY, AUGUST 26, 1879. 



The following Papers were read : — 



1. On some points in connection with Agricultural Chemistry. 

 By Dr. J. H. Gilbert, F.B.S. 



Dr. Gilbert stated that in the experiments of Mr. Lawes and himself, conducted 

 on the farm of Mr. Lawes, at Rothamsted, Herts, wheat had now been grown for 

 thirty-six years in succession on the same land ; barley for twenty-eight years in 

 succession, oats for nine years, root crops for more than thirty years, beans for more 

 than thirty years, and they had experimented on the mixed herbage of grass land 

 for twenty-four years. They found minor distinctions in the manurial requirements 

 of different plants of the same natural family, but very great distinctions in the 

 requirements of plants of different natural families. The gramineous crops are very 

 low in their percentage of nitrogen, and yield but a small quantity of it per acre. 

 Yet nitrogenous manures are very effective when applied to such crops. Legumi- 

 nous crops, on the other hand, are very high in their percentage of nitrogen, and 

 yield a large amount of it per acre. Yet nitrogenous manures are of little avail to 

 these plants, and potass manure is especially effective. The difference in the manure 

 requirements of plants of other natural families was also pointed out. Much more 

 complicated, however, was the problem when experiments were made upon the 

 mixed herbage of grass land, where they might have fifty or more species growing 

 in association, representing perhaps twenty natural families. It was at once found 

 that the manures which most favoured gramineous crops separately grown on arable 

 land brought forward the gramineous plants of the mixed herbage. Those, on the 

 other hand, which favoured the leguminosae, grown separately, on arable land, 

 brought forward the legiuninosse in the mixed herbage. Somewhat similar results 

 occurred with the plants of other natural families. Hence, the twenty different plots 

 in those experiments soon showed as many distinct floras. Tables were exhibited 

 illustrating the variation in the number of species, their percentage by weight, and 

 the amounts which the different natural families yielded per acre. With the great 

 difference, not only in the flora, but also in the character of development of the 

 plants, there was the greatest possible difference in the chemical composition. The 

 dry matter of the mixed herbage contained in some cases 1£ time as much nitrogen 

 as in others. The percentage of potass in the produce varied as one to two, and 

 the amount of potass yielded per acre as one to five in the different experiments ; 

 and there were considerable differences among the other constituents. The produce 

 of the respective natural families possessed its own normal composition within certain 

 limits. Yet this was varied immensely according to the conditions supplied, and 

 the character of the produce grown. Thus, the ash of the gramineous produce 

 showed a variation in the percentage of potass of from about 24 to about 40 ; the 

 ash of the leguminous produce from 12 to 33 ; and that of the miscellaneous pro- 

 duce from 17 to 37. One point of especial interest was the difference in the 

 amount of nitrogen yielded by the plants of the different natural families. It was 



