178 



WEIGHTS OF ASH LEFT BY DIFFERENT SPECIES. 



the growing plant those decaying vegetable matters which are most 

 likely to supply it with organic food. 



For the full establishment of this fact, we are indebted to Sprengel. 

 Others, as De Saussure, have published many important and very use- 

 ful analyses of the inorganic matters left by plants, but for the illustra- 

 tion of the important practical bearing of this knowledge of their inor- 

 ganic constituents on the ordinary processes of agriculture, we are, I 

 believe, in a great measure indebted to the writings and numerous ana- 

 lytical researches of Sprengel. 



It is difficult to conceive the extent to which the admission of the es- 

 sential nature and constant quality of the inorganic matter contained in 

 plants, must necessarily modify our notions and regulate our practice in 

 every branch of agriculture. It establishes a clear relation between the 

 kind and quality of the crop, and the nature and chemical composition 

 of the soil in which it grows — it demonstrates what soils ought to con- 

 tain, and, therefore, how they are to be improved — it explains the effect 

 of some manures in permanently fertilizing, and of some crops in per- 

 manently impoverishing the soil — it illustrates the action of mineral 

 substances upon the plant, and shows how it may be, and really is, in a 

 certain measure, fed by the dead earth : — over nearly all the operations 

 of agriculture, indeed, it throws a new and unexpected light. Of this, I 

 am confident, you will be fully satisfied when I shall have discussed the 

 various topics I am to bring before you in the present part of my lectures. 



§ 1. Of the relative proportions of inorganic matter in different 

 vegetable substances. 

 As above stated, the inorganic matter contained in different vegetable 

 productions varies from I to 12 per cent, of their whole weight. The 

 ifollowing table exhibits the weight of ash left by 100 lbs. of the more 

 commonly cultivated plants — according to the analyses of Sprengel 

 [Ckefnie, vol. ii., passim] : — 



Undried. Dried in air. * 



Potato 0-83 lbs. 2-65 lbs. 



Turnip 0-63 7-05 



Do. white . ... 0-8 J. 



Carrot 0-66 5-09 



Parsnip 0-82 4-34 



Leaf of Potato . . 4-79 



Turnip ... 1-8 2-91 



do. white . 2-18 J. 



• Carrot . . . 1-98 10-42 



Parsnip . . . 3-00 15-76 



Cabbage . . 0-53 7-55 



Grain of Per ct, 

 Wheat . . 1-18 lbs. 

 Rye . . . 1-04 

 Barley . . 2-35 

 Do. dried at 212, 2-52 J 

 Oats . . . 2-58 

 Field Beans . 2-14 

 Peas . 2-46 



Dry straw of 

 Wheat 

 Oats . 

 Barley . 

 Rye . 

 Beans . 

 Peas . 



Perct. 

 3-51 lbs. 

 5-74 

 5-24 

 2-79 

 3-12 

 4-97 



Lucerne 

 Red Clover 

 White Clover 

 Rye Grass . 



Green. 

 2-58 lbs. 

 1-57 ' 

 1-74 

 1-69 



In hay. 

 9-55 lbs 

 7-48 

 9-13 

 5-3 



Of the substances in this column the potato lost by drying in the air 69 perct. of water, 

 the turnip 91, the carrot 87, the turnip leaf 86, the carrot leaf, the parenip, and the parsnip 

 leaf, each 81, and the cabbage leaf 93 per cent. 



