dourless substance, portable, and capable of
being placed upon a candlestick, or burned in a lamp. Wax, tallow,
and oil, are combustible gases in a solid or fluid form, which offer
many advantages for lighting, not possessed by gas: they furnish, in
well-constructed lamps, as much light, without requiring the
expensive apparatus necessary for the combustion of gas, and they
are generally more economical. In large towns, or such establishments
as hotels, where coke is in demand, and where losses in stolen tallow
or oil must be considered, together with the labour of snuffing
candles and cleaning lamps, the higher price of gas is compensated.
In places where gas can be manufactured from resin, oil of turpentine,
and other cheap oils, as at Frankfort, this is advantageous so long
as it is pursued on small scale only. If large towns were lighted in
the same manner, the materials would rise in price: the whole amount
at present produced would scarcely suffice for two such towns as
Berlin and Munich. But no just calculation can be made from the
present prices of turpentine, resin, &c., which are not produced
upon any large scale.

[Footnote 1: Malter--a measure containing several bushels, but
varying in different countries.]

[Footnote 2: Klafter--a cord, a stack, measuring six feet every
way.]

LETTER V

My dear Sir,

Until very recently it was supposed that the physical qualities of
bodies, i.e. hardness, colour, density, transparency, &c., and still
more their chemical properties, must depend upon the nature of their
elements, or upon their composition. It was tacitly received as a
principle, that two bodies containing the same elements in the same
proportion, must of necessity possess the same properties. We could
not imagine an exact identity of composition giving rise to two
bodies entirely different in their sensible appearance and chemical
relations. The most ingenious philosophers entertained the opinion
that chemical combination is an inter-penetration of the particles
of different kinds of matter, and that all matter is susceptible of
infinite division. This has proved to be altogether a mistake. If
matter were infinitely divisible in this sense, its particles must
be imponderable, and a million of such molecules could not weigh
more than an infinitely small one. But the particles of that
imponderable matter, which, striking upon the retina, give us the
sensation of light, are not in a mathematical