THE SOUTHE 



the extent of absorption is likewise af- 

 fected by the strength of the- solution 

 employed. 



A few examples may illustrate the ex- 

 tent to which ordinary soils remove am- 

 monia and potash from their combina- 

 tions with different acids : — 



1000 grains of a light-red soil, from 

 Mr. Pusey's estate in Berkshire, which 

 was found to absorb 1-570 grains of free 

 ammonia per 1000 grains of soil, absorbed 

 from muriate of ammonia 1-966 grains of 

 ammonia. Another soil, 1000 grains of 

 which were found to absorb 3-438 grains 

 of free ammonia, likewise removed a 

 larger quantity of ammonia from the mu- 

 riate for 1000 grains absorbed ; from mu- 

 riate of ammonia, 3-478 grains of ammo- 

 nia, or nearly the same quantity as in 

 the experiment with free ammonia. In 

 this instance the absorptive power of the 

 soil thus appears the same, whether the 

 ammonia be in a free state, or united to 

 muriatic acid. 



1000 grains of subsoil clay from Corn- 

 wall, (coloured red by oxide of iron,) ab- 

 sorbed from muriate of ammonia -818 

 grain of ammonia, or a much smaller 

 quantity than that in the preceding expe- 

 riment. 



1000 grains of white clay, from the 

 plastic clay formation, absorbed from mu- 

 riate of ammonia 2 847 grains of ammo- 

 nia, and with a solution of the same salt, 

 but of a different strength, 1000 grains of 

 the clay were found to absorb 2-078 grains 

 of ammonia. 



Digested with different solutions of ni- 

 trate of potash, the same white clay ab- 

 sorbed, 



In one experiment, 4*366 grains of potash. 

 In a vsecond " 4 980 " 



In all these experiments, the acids of 

 the salts employed were found, in the fil- 

 tered solutions, in combination with lime, 

 and it was, therefore, natural to suspect 

 the carbonate' of lime originally present 

 in the soil to play an important function 

 in the absorption of ammonia, potash, &c. ; 

 but direct experiments with carbonate of 

 lime added to the soil, in order to ascer- 

 tain if its power to absorb ammonia would 

 be increased or not, have shown to Pro- 

 fessor Way that carbonate of lime is not 

 the agent to which the fixation of ammo- 

 nia is due, and that its addition, conse- 



RN PLANTER. 389 



quently, does not augment the power of 

 the soil to* absorb ammonia or potash. 

 Sufficient evidence, we think, is furnished 

 in these experiments to show that the 

 power of soils, of which we are speaking, 

 is not the same as that exhibited by po- 

 rous substances, that it is not due to mere 

 surface attraction, and, in short, that it 

 cannot be referred to any previously 

 known physical property possessed by 

 soils, but that it is a power sui generis. 

 Not content, however, to have proved the 

 existence of a hitherto unsuspected power 

 in soils, Professor Way endeavoured to 

 find out the true cause of this remarkable 

 action, and happily his labours in that di- 

 rection, prosecuted with most praisewor- 

 thy zeal, perseverance, and talent, have 

 been crowned with success. 



After having proved experimentally that 

 the power of soils to absorb manuring sub- 

 stances is not due either to the presence of 

 sand, carbonate or silicate of lime, of 

 oxide of iron, or alumina, neither can 

 it be referred to the organic matter, 

 in the soil, nor to the silicate of 

 alumina, or pure clay, in the soil, Pro- 

 fessor Way was fortunate enough to dis- 

 cover a new class of remarkable com- 

 pounds which possesses the power under 

 discussion in a high degree. These com- 

 pounds, in the language of the chemist, 

 are called double silicates; and it is to their 

 presence in all fertile soils that Professor 

 Way refers the peculiar and hitherto un- 

 known action described above, which all 

 such soils exhibit in a smaller or less de- 

 gree. Before proceeding further in our 

 inquir}', it will be necessary to explain 

 briefly what is meant by the term double 

 silicates. When pure silicious sand or 

 powdered quartz-rock, or flints, or any 

 other variety of the substance which the 

 chemist calls silica, or silicic acid, is 

 fused at a high temperature with pot- 

 ash, soda, lime, or magnesia, &c, it re- 

 sults in each case in a chemical combina- 

 tion between the silica and the substance 

 with which it has been fused. The com- 

 binations thus produced are called sili- 

 cates. Thus the compound of silica 

 with potash is a silicate, that of silica 

 with soda is another, and silicate of lime, 

 is a compound of silica with lime ; and as 

 each of these compounds contains but 

 one substance united to silica, they are 

 distinguished from other similar com- 



