Society,' 1891;
'Chemical News,' 1893.

APPENDIX TO CHAPTER XIV.

NOTE (p. 404).

For those more particularly interested, we append a full analysis of the
slag, taken from Messrs Stead and Ribsdale's paper in the 'Journal of
the Iron and Steel Institute,' 1887, vol. i. p. 222:--

Lime 41.58
Magnesia 6.14
Alumina 2.57
Peroxide of iron 8.54
Protoxide of iron 13.62
Protoxide of manganese 3.79
Protoxide of vanadium 1.29
Silica 7.38
Sulphur } .23
Calcium } .31
Sulphuric anhydride .12
Phosphoric acid 14.36
-----
99.93

CHAPTER XV.

POTASSIC MANURES.

_Relative Importance._

In Chapter VI. we pointed out that of the three manurial ingredients
potash was the one most abundantly occurring, and that, consequently,
the necessity of adding it in the form of an artificial manure existed
less frequently than in the case of nitrogen or phosphoric acid. It was
further pointed out that, under the ordinary conditions of agriculture,
a greater restoration to the soil of the potash removed in the crops was
made in the straw used in farmyard manure than was the case with regard
to the other two ingredients. Despite these facts, there are many cases
where the addition of potassic manures is of the highest importance in
increasing plant-growth. It will be well, therefore, to devote a little
space to considering our different potassic manures and their respective
action.

_Scottish Soils supplied with Potash._

Potassic manures are not so valuable in this country since experience
has shown that most Scottish soils are abundantly supplied with this
manurial ingredient. Moreover, under the conditions of most European
farming, there seems to be a steady gain to the soil of potash. In
America, however, the action of potash as a manure seems to be more
strikingly illustrated. Indeed, wherever forage crops or straw are sold
off the farm in large quantities, or where beets, cabbages, carrots,
potatoes, onions, &c., are also grown in large quantities, the necessity
for potash manuring generally arises.

_Sources of Potassic Manures._

The value of potash as a manure first came to