leaden
glaze of the porcelain ones. Hence, where silver cannot be had, iron
vessels are preferable to tinned copper ones; or those made of tinned
iron-plates in the common tin-shops, which are said to be covered with pure
or block tin.

6. Another circumstance, which facilitates the nourishment of mankind, is
the mechanic art of grinding farinaceous seeds into powder between
mill-stones; which may be called the artificial teeth of society. It is
probable, that some soft kinds of wood, especially when they have undergone
a kind of fermentation, and become of looser texture, might be thus used as
food in times of famine.

Nor is it improbable, that hay, which has been kept in stacks, so as to
undergo the saccharine process, may be so managed by grinding and by
fermentation with yeast like bread, as to serve in part for the sustenance
of mankind in times of great scarcity. Dr. Priestley gave to a cow for some
time a strong infusion of hay in large quantity for her drink, and found
that she produced during this treatment above double the quantity of milk.
Hence if bread cannot be made from ground hay, there is great reason to
suspect, that a nutritive beverage may be thus prepared either in its
saccharine state, or fermented into a kind of beer.

In times of great scarcity there are other vegetables, which though not in
common use, would most probably afford wholesome nourishment, either by
boiling them, or drying and grinding them, or by both those processes in
succession. Of these are perhaps the tops and the bark of all those
vegetables, which are armed with thorns or prickles, as gooseberry trees,
holly, gorse, and perhaps hawthorn. The inner bark of the elm tree makes a
kind of gruel. And the roots of fern, and probably of very many other
roots, as of grass and of clover taken up in winter, might yield
nourishment either by boiling or baking, and separating the fibres from the
pulp by beating them; or by getting only the starch from those, which
possess an acrid mucilage, as the white briony.

7. However the arts of cookery and of grinding may increase or facilitate
the nourishment of mankind, the great source of it is from agriculture. In
the savage state, where men live solely by hunting, I was informed by Dr.
Franklin, that there was seldom more than one family existed in a circle of
five miles diameter; which in a state of pasturage would support some
hundred people, and in a state of agriculture many thousands.