indeed, lie some hard questions; but all that is necessary is easy, and
the discussion of difficulties, although it may well repay the labour,
is by no means essential.

The chief use of leaven in the preparation of bread is, as I understand,
to produce a mechanical effect. A certain chemical change is caused in
the first instance by fermentation in the nature of the fermented
substance, and for the sake of that change the process is in certain
other manufactures introduced; but along with the chemical change which
takes place in the nature of the substance, a mechanical change is also
effected in its form, and for the sake of this latter and secondary
result fermentation is resorted to in the baking of bread. The moist,
soft, yet dense mass of dough, is by fermentation thrown into the form
of a sponge. Owing to the consistence of the material, the openings made
by the ferment remain open, and consequently the lump, which would
otherwise have been solid, is penetrated in every direction by an
innumerable multitude of small cavities. Through these the heat in the
oven obtains equal access to every portion of the dough; and thus,
though the loaf is of considerable thickness, it is not left raw in the
heart. Other methods, essentially different from fermentation, are in
modern practice adopted in the preparation of bread; but by whatever
means channels may be opened for the admission of heat to every particle
of the dough, the result is practically the same as that which is
obtained by leavening. The operator converts the mass of solid dough
into swollen, light, porous, spongy leaven, by introducing into it a
small quantity of matter already in a state of fermentation. It is the
nature of that substance or principle to infect the portion that lies
next it; and thus, if the contiguous matter be a susceptible conductor
like moistened flour, it spreads until it has converted the whole mass.
The knowledge of this process is not so universal amongst us as it was
then in Galilee, or is still in many countries, because baking by
fermentation, especially in the northern division of the island, is not
much practised in private families. In countries where bread is prepared
by that method, and every family prepares its own, the process is, of
course, universally familiar.

The three measures of meal, which together make an ephah, were the
understood quantity of an ordinary batch in the economics of a family,
and as such are severa