which a current of electricity is passing.

CHAPTER XIII.

SOAP, CANDLES, TALLOW TREE, SPERMACETI, WAX, MAHOGANY, INDIAN
RUBBER OR CAOUTCHOUC, SPONGE, CORAL, LIME, CARBON, OXYGEN, NITROGEN,
GAS, HYDROGEN, CHALK, AND MARBLE.

Of what is Soap composed?

Of soda or potash, and various oily substances; it is so useful for
domestic and other purposes, that it may be regarded as one of the
necessaries of life; immense quantities of it are consumed in all
civilized countries. Soft soap is generally made of a lye of
wood-ashes and quicklime, boiled up with tallow or oil; common
household soap of soda and tallow, or of potash and tallow; when
potash is used, a large portion of common salt, which contains soda,
is added to harden it. The finest white soaps are made of olive oil
and a lye consisting of soda and quicklime; perfumes are sometimes
added, or various coloring matters stirred in to give the soap a
variegated appearance. The ancient Greeks and Hebrews appear to have
been acquainted with the art of making soap, or a composition very
similar to it; and also the ancient Gauls and Germans. A soap-boiler's
shop, with soap in it, was found in the city of Pompeii, in Italy,
which was overwhelmed by an eruption of Mount Vesuvius, A.D. 79.

What is Soda?

Soda, or barilla, is obtained from the ashes of marine plants, and by
the decomposition of common salt; its great depository is the ocean,
soda being the basis of salt. The marine plants from which the soda is
obtained, are endowed with the property of decomposing the sea-salt
which they imbibe, and of absorbing the soda which it contains. It is
found native in Egypt, and is there called _natron_; a name similar to
that which it bore among the Jews and Greeks.

_Depository_, store-house, place where anything is lodged.

_Imbibe_, to drink in, to absorb.

Of what are Candles made?

Of Tallow, which means animal fat melted and clarified, that is,
cleansed or purified from filth. Tallow is procured from many animals,
but the most esteemed, and the most used, is that made from oxen,
sheep, swine, goats, deer, bears, &c.; some of which tallows or fats
are used in medicine, some in making soap, and dressing leather;
others in the manufacture of candles, &c. For the last-mentioned
article, that of sheep and oxen is most used; candles of a better sort
are likewise made of wax and spermaceti. Candles are kept burning by
means of a wick of cotton or rus