The Sun.
London, England, 1830-01-23 00:00:00

ARITHMETIC.

PINNOCK'S ARITHMETICAL TABLES of Money,
Weights, and Ale3sures; with Questions fur Examina-
tion, Notes, tic. improved. Price 6d.

CATECHISM of'ARITHMETIC ; containing a con-
cise Explanation of its most useful Rules and Examples.
Price 9d.

PINNOCK'S PRINTED CIPHERING BOOK,
No. 1 , containing easy Exercises in the First Rules of
Arithmetic. Price IP.

PINNOCK'S PRINTED CIPHERING BOOK,
No. 2 ; containing the fire principal Rules of Arithmetic,
both simple and Compound ; to which are annexed, for
the Improvement of the Pupil, numerous Exercises upon
each Rule. Price 3s.

PINNOCK'S PRINTED CIPHERING-BOOK,
No. 3 ; intended ac a Sequel to the preceding ; and c
il-
cuiatcd to qualify the Student for the more advanced
Rules of Arithmetic. Price 3s.
A KEY to the CIPHERING-BOOKS, Nos. I, 2,
an:l 3, containing Six Answers to each Sum. Price 34.
A short SYSTEM of PRACTICAL ARITHMETIC.
By ROBERT FRAITEIL Price 2s. 6d.
BOOK-KEE PING.
A❑ INTRODUCTION to BOOK-KEEPING; com-
prising Inland and Foreign Trade, arranged by Single
Entry ; Italian Method of Double Entry ; and the pre-
sent Practice of the Counting-house ; with a Comparison
of these three Methods. To which are subjoined, Qutlies
and Answers on Merchants' Accounts, Book-kceping, and
Bilk. With engraved Forms, &c. Designed for iichools
and Counting-houses. By C. MORRISON, Accountant.
Glasgow. Second Edition, Svo. price Ss. bound.

Much interest has lately been excited by the
revival of an ON custom well known and practised in North
America, where the winters are much more severe than in
this country. It is more than half a century since I wit-
nesst4 the fact of the Americans throwing salt into their
common oaken-pumps to liberate the frozen pump-box.
The vulgar impression was, that salt was of a very heating
nature, and, like hot-embers,:would thaw the ice. It i 5
now become very common, and found very convenient, to
make use of salt for dissolving snow and ire on the side-
ways; bat many of the recent explanations have been
quite as absurd as the above, and more obscure. Like all
others of Nature's operations, the true cause is extremely
simple. It is known that ice and salt have not so great a
capacity for heat as liquid water. The thermometers no
more indicate the specific quantity of heat in different bodies
than the lady's diamond necklace indicates the depth of her
Lord's purse. Now, teeter at 32 temperature will disen-
gage 140 degrees of heat before it will crystallize. This
is known by the following experiment :—Let one pound
of ice, at 32 degrees temperature be immersed in one
pound of water at 140 degrees temperature, awl when the
ice is completely dissolved, the whole will be at a tempe-
rature of 30 degrees, evidently showing that 140 degrees
of heat had entered the pound of ice to cause it to become
a liquid. Salt ham also less capacity for heat than water
though how much less I cannot precisely say ; but to un-
derstand the operation of salt melting ice, it is not im-
portant. Strong brine will remain liquid until its tempe-
rature has settled below zero. Such is the strong attrac-
tion between ice and salt, that they will become a
liquid, if the temperature of the atmosphere is above
the freezing point of briae—say, if above zero. This
being the ease, as soma as the salt is brought in
contact with the ice or scow, liquefaction commences,
and the heat is borrowed from the atmosphere and
surrounding bodies. This operation continues until lique-
faction is complete, which, together with the atmosphere,
beceines of the same temperature.—e. From a Correspoaderat.