essed, its surface will oxidate equally, provided all
its parts are equally heated. In the process of converting this disc
into a coin, the _sunk_ parts have obviously been _most compressed_
by the prominent parts of the die, and the _elevated_ parts _least
compressed_, the metal being in the latter left as it were in its
natural state. The raised letters and figures on a coin have therefore
less density than the other parts, and these parts oxiditate sooner or
at a lower temperature. When the letters of the legend are worn off by
friction, the parts immediately below them have also less density than
the surrounding metal, and the site as it were of the letters therefore
receive from heat a degree of oxidation, and a colour different from
that of the surrounding surface. Hence we obtain an explanation of the
revival of the invisible letters by oxidation.

* * * * *

THE GATHERER.

* * * * *

_Locomotive Engines_ have been established on the rail-roads near
Philadelphia. The distance of 16-1/2 miles was performed by one of them
going in an hour and thirteen minutes, returning (laden both ways) in an
hour and eight minutes. The last mile was done in three minutes.

_Blacking._--Shoes, among the classical ancients, were cleaned by a
sponge; in the middle ages, by washing. Oil, soap, and grease were the
substitutes for blacking, which was at first made with soot, but shone
with a gloss.

_Cool Tankard._--The custom of the Lord Mayor drinking a "cool
tankard" with the governor of Newgate, on his Lordship's way to proclaim
Bartholomew Fair, is better known to our readers than the precise contents
of the said tankard. In olden times the "cool tankard" was, or nearly
coincided with, the wine mixed with _Burrage_, (so the translators
call the herb) of Plutarch, and the _Herbosum Vinum_ of Du Cange. In
all probability, the "cool tankard" of our times implies a well-appointed
_dejeune a la fourchette_.

_Hanging_--though as a punishment for thieves, ascribed to the reign of
Henry I., occurs in a charter of Edgar. In hanging for public spectacle,
an iron hoop with a strong chain was put round the body; but the chain
was longer than the halter, so that when the latter was cut, the hoop
slipped to the armpits, and left them suspended. When criminals escaped,
an image of them was often hung up for several days; whence our hanging
in effigy.

_Elections._--Br