THE- FARMERS' REGISTER. 



351 



merely of ihe elenienta mentioned, it would 

 va|)orize, be enlirely dissipatod, and nothing would 

 belel't; but very lew piunie will do this. JSonic 

 of llie elements of plants will do it, as starch, 

 sugar, and the essential oiU- ; but generally we 

 find, that alter the burning away ol a plant, there 

 is an ash lel't. In coals, which are but vegetables 

 translbnned, we (ind llie value ol' the coal depends 

 upon the greater or less quaniity of ashes left ; 

 and this asli wc will term the inorganic princi[)le 

 of vigelables. This consists ol potash, soda, 

 lime, magnesia, some ol' the metallic oxides, 

 phosphoric, sulphuric, and other acids, clilorine, 

 iodine, and 1 need hardly enumerate them all ; 

 but there are a number ol fixed elements, capable 

 ol existing in a solid Ibrm, unaiierable and un- 

 changeable by heat. (He exhibited a quantity 

 of ashes obtained from burning six ears of corn, 

 after thrashing, and without the wheat; in addi- 

 tion to a quantity of soluble matter, which had 

 been dissolved.) In reading the vvoiks of the 

 older physiologists, we meet the statement, "Such 

 a plant contains aliiilesoda and a little magne- 

 sia," without specitying proportions, or any stress 

 being laid upon the fact. But more accurate in- 

 vestigations have shown, that there are certain 

 relaiive proportions between the quantity of these 

 fixed materials and the plant itself; that, in pro- 

 portion as these exist in the soil or the plant, its 

 developement is more or less perlect. If a fiirmer 

 attempt to grow wheat on a soil containing neither 

 flint nor potash, he may get wheat, but it will not 

 stand, the stems will not support it; because the 

 stalk of wheat contains a species of glass — silex 

 in combination with potass. He would have no- 

 thing in the ear, unless the soil were provided 

 with a salt called the phosphate of magnesia and 

 ammonia. This has been tried in the mosses,* 

 which contain hu)nus enough, but without the 

 addition of some compost they never bear. In 

 the tribe of plants called equisetacecB, the stem 

 contains large quantities of silica. The Dutch 

 rush contains so much ihat it is used lor the pur- 

 pose of polishing; and it is (bund in large quan- 

 tities in some tropical plants. The bamboo in 

 some of the joints contains absolute nodules of a 

 substance consisting of 70 per cent, of silica, and 

 30 per cent, of potash. How came they there? 

 There has been some controversy upon this sub- 

 ject among chemists ; and one analysis has been 

 made io show, that it could not be a permanent 

 proportion, inasmuch as two pine trees, which 

 grew in difierent situations, contained different 

 proportions. Liebig took these analyses, com- 

 pared them together, and then introduced — trium- 

 phantly I think — the principle of equivalents, laid 

 down by our venerable townsman, Dr. Dalton, 

 showing that although the quantities appear very 

 dissimilar, yet in their proportions they are ex- 

 actly the same, although the data were taken 

 from a hostile source. Two pine trees were taken, 

 one growing on Mont Breven, and the other on 

 Mont La Salle. The first contained potash, lime, 

 and magnesia, and the sum of the carbonates 

 of these amounted to 56.71 per cent, in the ashes ; 

 whilst those of the pine grown on Mont La Salle 

 contained 58.55 of these carbonates ; but this 

 latter contained only potash and lime. In the 

 first the quantities were carbonate of potash 3.60, 



♦ Peat soils.— Ed. F. R. i 



carbonate of lime 46.34, carbonate of magnesia 

 6.77; in the second carbonate of potash 7.36, car- 

 bonate of lime 51.19. So that the one contain- 

 ing no magnesia contained more lime and more 

 potash; and when we examine the equivalents — 

 the proportions required to neutralize an acid — 

 we find them in Ihe one to amount to 9.01, in the 

 oiher to 8.95, bein<r a dilference of only .06 (six 

 hundredths,) a dilierence of weight which (ew 

 scales would detect. Liebig took another analy- 

 sis in which the disproportions are much tfrealer. 

 He look two fir-trees, one growing in Norway, 

 and the other at Allevard, in France. That in 

 France contained potash, soda, lime, and mag- 

 nesia; the sum ol these carbonates was 49.5 ; 

 while that ol'the carbonates found in the fir grown 

 in Norway was 51.45 ; yet these, when reduced 

 to the equivalents in which they combine with 

 acids, were found to be 11.62 and 11.47; from 

 which result Liebig is disposed to infl?r, that the 

 presence of these elements is not accidental ; but 

 that ihey form a certain proportion, and enter into 

 that proportion in the ratio of their equivalents. 

 Now from what sources are these matters de- 

 rived? Take a sandy heath, which contains, to 

 all appearance, nothing but sand, and where the 

 most expert analyst, will detect nothing else ; no 

 humus whatever, and, if you attempt to grow 

 wheat upon this heath, there will be no crop; 

 But, if on this heath plants are grown which 

 require but liille of the inorganic principle, and 

 these are destroyed either by decay or combustion 

 it is found in practice that the heath acquires ler- 

 tilitv. Take, for example, the Luneberg Heath,, 

 in Germany, which is covered with heath-plants 

 generally, especially the erica vulgaris. Every 

 thirty or fbriy years the practice is to burn down 

 all the vegetable growth on the surface, to let the 

 ashes sink into the ground, and then to sow 

 wheat ; and thus these [)lants, which have, for 

 the space of forty years, been constantly collecting 

 a little of these elements, when burned, contained 

 in their ashes the product of that number of 

 years' growth ; which, when returned into the 

 soil, is sufficient lor one crop of plants which re- 

 quire a good large proportion ol' these elements. 

 In the neighborhood o( Heidelberg, one of the 

 perquisites of the woodcutters, after lelling and 

 clearing timber, is to be allowed to burn the 

 roots, stumps, twigs, and leaves, and to raise one 

 year's produce from the ground. They do eo, 

 and get one good crop; lor, whatever the trees 

 and plants collect goes on accumulating, and then, 

 by destroying the carbonaceous parts by fire, the 

 inorganic products are returned to the soil, and 

 provide for one year's growth of wheat. Does 

 not this show us what is meant by exhausting a 

 soil? If wheat is grown year after year on the 

 sanie soil, it is (bund that the crop becomes less 

 and less productive. And why ? Because, with 

 every crop of wheat, so much of the inorganic 

 elements is removed or taken away from the 

 ground; therefore, in order to allow this ground 

 to recover these inorganic elements, it is necessa- 

 ry to resort either to the now exploded (?) system 

 of allowing it lo remain fallow, or to a rotation 

 of crops ; which, we shall show, will furnish 

 ground with potash and lime. But how does a 

 soil happen to contain potash originally? All 

 soils are formed from the disintegration of the 

 harder rocks ; they gradually accumulate in the 



