Perkins

3676

Perpetuity

making nails. He greatly improved the
process for engraving bank notes, and in
1814 removed to Philadelphia and entered
the business of bank-note engraving and
printing. In iSiS he settled in England, and
established a bank-note printing business. He
introduced many improvements in steam en-
gines and printing presses, in printing proc-
esses and in engraving.

Perkins, Thomas Handasyd (1764-
1854), American philanthropist, was born in
Boston, Mass. From 1805 he served in one or
the other houses of the Mass, legislature for
many years. He gave his house and lot in
Boston for the Perkins Institution for the
Blind, besides aiding the Bunker Hill Monu-
ment project. Mr. Perkins was a principal
organizer of the Quincy Railroad, the first
in the U. S.

Perlitic Structure, in volcanic rocks, con-
sists in the presence of small concentric
cracks, along which the rock readily breaks
down, yielding rounded pearl-like fragments.
Rocks having this structure are often called
Ferities.

Perm, town and river port in Soviet
Russia, 900 m. by water e. n.e. of Moscow,
and on the Kama R. It was formerly a de-
pot for convicts bound for Siberia, and is
now the center of the large transit trade be-
tween Central Russia and Siberia; p.85,000.

Permanganic Acid, HMnO.i, is unknown
in the pure state, but can be obtained as a
crimson, strongly acid solution by decom-
posing barium permanganate with dilute sul-
phuric acid.

Permutations and Combinations, the
branch of algebra which has to do with the
simpler problems of arrangement. Let there
be, say, ten objects—for example, ten boys
in a class. In how many ways may these
boys be arranged in groups of four? If no
regard be taken of the order in each group,
then the problem is one of combinations; but
if regard be had to the order, the problem
becomes one of permutations. The theory of
permutations and combinations has many
important applications in the discussion of
series, probability, and statistics*

Pernambuco, state, Brazil, on Atlantic
coast. The interior is mountainous, rising to
over 3,000 ft. In the coast lands known as
the Mata are plantations of sugar-cane and
cotton; coffee, tobacco, and rice are also
grown. The fruits of Pernambuco are fa-
mous. Recife is the capital. Area, 49,570 sq.
m.; p. 2,900,000.

Pernambuco, d'y, state of Pernambuco,
Brazil.

Peronne, tn., France, dep. Somme, on riv.
Somme, 30 m. e. of Amiens. Here Louis XL.
was forced to sign a treaty with Charles the
Bold of Burgundy in 1468. During the World
War Peronne was occupied by German
troops, but in March 1917, they were driven
out by the British. A year later the Germans
recovered the town, but lost it to the Aus-
tralians in September 1918; p. 4,500.

Perpetual Motion. According to the doc-
trine of the conservation of energy it is not
possible to do work without expenditure of
energy in some form. Nevertheless many
forms of apparatus have been devised by
which the inventor believed it possible to
gain work without expenditure of effort, Jf
a system could be devised so as to be able
to keep up its motion perpetually and at the
same time to do useful work, the law of the
conservation of energy would be disproved
and the perpetual motion discovered. The
true perpetual motion must be carefully distin-
guished from an apparent perpetual motion,
in which a system may be made to continue
moving indefinitely, but only because it is
able to tap some more or less hidden source
of energy.

Perpetuities, Rule against. A rule of law
designed to prevent the limitation of future
estates in real and personal property, subject
to such contingencies that they will not nec-
essarily become vested within a certain peri-
od, considered to be a reasonable time. This
period varies in different states, and the sub-
ject is generally regulated by statutes. This
name is also commonly applied to statutes
prohibiting the suspension of the power of
alienation of property beyond a fixed period.
The English rule provides that future estates
must vest within a life or lives in being and
twenty-one years, and this is followed in
many of the United States. Several states
have fixed the period at two lives in being
and twenty-one years, and in New York and
a few other states it is two lives in being
and the period of a minority. The rule
against perpetuities applies to estates in trust
as well as legal estates. Consult Gray, Rules
Against Perpetuities.

Perpetuity, When property is so held that
no one can dispose of the absolute ownership
thereof it is said to be held in perpetuity.
Various rules have been passed to prevent
perpetuities for any great length of time,
The rule applies to personal property as well