[123] See Appendix, Note I., p. 210.

[124] See Appendix, Note II., p. 211.

[125] These results, as indeed all soil percentages, are calculated on
the soil in a dry condition.

APPENDIX TO CHAPTER V

NOTE I. (p. 201).

COMPOSITION OF APATITE (Voelcker).

(_Krageroee, Norway._)

Lime 52.16
Phosphoric acid 41.25
Chlorine 4.10
Fluorine 1.23
Oxide of iron 0.29
Alumina 0.38
Potash and soda 0.17
Water 0.42
------
100.00
======

Apatite is found in considerable quantities in America, Germany, France,
Spain, Hungary, Norway, and Great Britain. According to Rose, apatite is
made up of three molecules of tribasic calcium phosphate (Ca(PO_4)_2),
combined with one molecule of calcium fluoride (Ca F_2) or one molecule
of calcium chloride (CaCl_2) respectively.

The composition of the pure mineral should be--

_Chlorapatite._
Per cent.
Calcium phosphate 89.38
Calcium chloride 10.62

_Fluorapatite._

Calcium phosphate 92.31
Calcium fluoride 7.69

NOTE II. (p. 203).

The following is a list of the commoner rocks in which the percentage of
phosphoric acid has been determined. The results are taken from analyses
by Nesbit, Schramm, Bergemann, Rose, Deherain, Handtke, Petersen,
Nessler, Muth, Fleischmann, Storer, and others:--

Per cent.
Felspar 1.7
Granite 0.09 0.25 0.58 0.68
Lava 1.21 1.8
Trachyte 0.30 0.66
Basalt 0.50 1.11
Porphyry 0.26
Marl 1.45 2.31 3.8
Calcareous stones 0.064 0.176
Dolomite 1.24
Lias chalk 1.39
Gneiss 0.18 0.78 1.51
Syenite 0.10
Dolerite 0.3 1.1 1.2
Diorite 0.5 0.69

CHAPTER VI.

THE POSITION OF POTASH IN AGRICULTURE.

We may, lastly, consider the position of _potash_ in agriculture, the
only ash ingredient of the plant, in addition to phosphoric acid, which
it is as a rule necessary to add as a manure.

_Potash of less Importance than Phosphoric Acid._

It is of far less importance than phosphoric acid, from the fact of its
much more abundant occurrence