472 WE. J. B. LAWES, DE. GILBERT, \\l> DR rrcii OS 



in the manner jusl indicated,a pol ofsi.il, prepared exactlj asfbi an experiment with a 

 plant, was submitted to the same conditions of air, temperature, moisture, >.V'-.. as the p 

 containing the experimental plants. The result \\;is. thai there was oo accumulatioii 

 combined Nitrogen. The resull with the matrix of pumice also showed, compared with 

 thai of the Boil-matrix, thai no error was to be feared from the influence of the latter in 

 absorbing and retaining combined Nitrogen already in connexion with the plant. 



For our purpose, pure volcanic pumice was used. It was powdered until the mass 

 quite fine and the largest pieces -were about the size of peas. This powder was subjected 

 to long washing in the same manner as the ignited soil. Lastly, it was dried ready tat 

 a final ignition before being used. 



B. — The Mineral Constituent* added to the prepared Soil. 



In most cases the necessary Mineral Constituents were supplied in the form of the 

 ash of the plant of the description to be grown. In a few instances, when- this was 

 not practicable, the ash of some other plant Avas selected. Weak solutions of sulpha' 

 and phosphates, as well as ash, were also sometimes used. 



In some instances the ash was obtained by burning a quantity of the entire plant 

 when in seed. In other cases, the seed and the rest of the plant being burnt separately, 

 a mixture of the two ashes was made in such proportion as to represent the composition 

 of the ash of the entire plant. 



Thus, in the experiments of 1857, for Wheat a mixture of one part of the grain-ash 

 and six parts of the straw-ash, for the Barley a mixture of one part of the grain-ash 

 and three parts of the straw-ash, and for Beans a mixture of one part of the corn-ash 

 and two parts of the straw-ash was used. In the experiments of 1858, the ash used for 

 these crops was obtained by burning the entire plant. For Clover, the ash of Clover- 

 hay was employed. 



In some instances of Leguminous plants the ash was saturated with sulphuric acid, 

 and then ignited, before being used. 



Each ash was burnt in a large shallow platinum dish, heated in a current of air. in 

 a cast-iron muffle. The burning w r as continued until all coaly matter had disappeared. 

 The ash was then preserved, but was always submitted to a final ignition before being 

 used. Examination failed to detect combined Nitrogen in any of the ashes so prepared. 



In order that the roots of the plants should, find an abundance of mineral matter at 

 the most active period of growth, it was desirable that the matrix should contain as 

 much of such matter as was consistent with healthy development. A consideration of 

 the chemical constitution of soils suggested a proportion of 0-8 to TO per cent, of ash; 

 and this was the quantity added to the matrix for the experiments of 1857 ; but for 

 those of 1858 only about half as much was employed. 



