are usually employed to decorate the summits of the
buttresses, and in the still later Perpendicular work the vertical faces
are all richly decorated with panelling.

BUTYL ALCOHOLS, C_4H_9OH. Four isomeric alcohols of this formula are known;
two of these are primary, one secondary, and one tertiary (see ALCOHOLS).
Normal butyl alcohol, CH_3.(CH_2)_2.CH_2OH, is a colourless liquid, boiling
at 116.8 deg., and formed by reducing normal butyl aldehyde with sodium, or by
a peculiar fermentation of glycerin, brought about by a schizomycete.
Isobutyl alcohol, (CH_3)_2CH.CH_2OH, the butyl alcohol of fermentation, is
a primary alcohol derived from isobutane. It may be prepared by the general
methods, and occurs in fusel oil, especially in potato spirit. It is a
liquid, smelling like fusel oil and boiling at 108.4 deg. C. Methyl ethyl
carbinol, CH_3.C_2H_5.CHOH, is the secondary alcohol derived from n-butane.
It is a strongly smelling liquid, boiling at 99 deg.. Trimethyl carbinol or
tertiary butyl alcohol, (CH_3)_3.COH, is the simplest tertiary alcohol, and
was obtained by A. Butlerow in 1864 by acting with zinc methyl on acetyl
chloride (see ALCOHOLS). It forms rhombic prisms or plates which melt at
25 deg. and boil at 83 deg., and has a spiritous smell, resembling that of camphor.

BUTYRIC ACID, C_4H_8O_2. Two acids are known corresponding to this formula,
_normal butyric acid_, CH_3.CH_2.CH_2.COOH, and _isobutyric acid_,
(CH_3)_2.CH.COOH. Normal butyric acid or fermentation butyric acid is found
in butter, as an hexyl ester in the oil of _Heracleum giganteum_ and as an
octyl ester in parsnip (_Pastinaca sativa_); it has also been noticed in
the fluids of the flesh and in perspiration. It may be prepared by the
hydrolysis of ethyl acetoacetate, or by passing carbon monoxide over a
mixture of sodium acetate and sodium ethylate at 205 deg. C. (A. Geuther,
_Ann._, 1880, 202, p.306), C_2H_5ONa + CH_3COONa + CO = H.CO_2Na +
CH_3.CH_2.CH_2.COONa. It is ordinarily prepared by the fermentation of
sugar or starch, brought about by the addition of putrefying cheese,
calcium carbonate being added to neutralize the acids formed in the
process. A. Fitz (_Ber._, 1878, 11 p. 52) found that the butyric
fermentation of starch is aided by the direct addition of _Bacillus
subtilis_. The acid is an oily liquid of unpleasant smell, and solidifies
at -19 deg. C.; it boils at 162.3 deg. C., and has a specific gravity of 0.9746 (0 deg.
C.). It is eas