Peaty manuring

1266. Inert peaty matter, tanners' spent bark, shavings of wood, and saw-dust, though they consist almost entirely of woody fibre, are of very little use as manures, unless they are mixed with lime or some other alkali which will render the humus which they form soluble in water. Tanners' bark, decaying slowly, and evolving considerable heat during the process, is useful as a hotbed.