gold, but the _rate_ of
expansion for gold is nearly twice (1-7/10) that of tin.

The capacity for absorbing heat varies with each metal; that of gold is
about twice (1-3/4) that of tin.

Tin has a scale hardness of about 4, on a scale of 12 where lead is
taken as the softest and platinum the hardest. (Dixon, "Vade Mecum.")

Tin has a scale hardness of about 2. (Dr. Miller.)

To fuse a tin wire one centimeter in diameter requires a fusing current
of electricity of 405.5 amperes. Up to 225 deg. C., the rise in resistance
to the passage of an electric current is more rapid in tin than in gold.
In some minerals the current follows the trend of the crystals.

Gold wire coated with tin, and held in the flame of a Bunsen burner,
will melt like a tin wire. At 1600 deg. to 1800 deg. tin boils and may be
distilled.

CHAPTER II.

The largest and most complete dental library in the world is owned by
Dr. H. J. McKellops, of St. Louis. Upon his cheerful invitation, the
writer visited that "Mecca," and through his kindness and assistance a
complete search was made, which resulted in obtaining a great portion of
the following historical facts with reference to the use of tin in
dentistry:

"In 1783 I stopped a considerable decay in a large double under tooth,
on the outside of the crown or near the gums, with fine tin foil, which
lasted for a good number of years." ("A Practical and Domestic Treatise
on Teeth and Gums," by Mr. Sigmond, Bath, England, 1825.)

"Fine tin foil or gold leaf may be injected into a cavity successfully,
and retained securely for many years." (Joseph Fox, Dover, England,
1802.)

"The statement has been made several times that tin foil was used in the
United States for filling teeth as early as 1800, at which time
dentistry began to be cultivated particularly as a science and art, and
was beginning to be regarded as of more importance than it formerly had
been. The writer has not found any record of its use in this country
earlier than 1809. Tin may often be employed with entire confidence. I
have seen fillings forty-one years old (made in 1809) and still perfect.
Several molars had four or five plugs in them, which had been inserted
at different periods during the last half-century. I prefer strips cut
from six sheets laid upon each other. If the foil is well connected, the
cut edges will adhere firmly; if they do not, the foil is not fit for
use." (Dr. B. T. Whitney, _Dental Register of th