The daily national Whig. [volume] (Washington, D.C.) 1847-1849, 1849-01-10
NATURAL PHILOSOPHY,

The Newark Daily Advertiser has the following
notes of lecture on Natural Philosophy, delivered
by Professor MArEs last week-the four general
truths Atom Attraction, Repulslon and Inertia, be-
ing under consideration;
The Density OF n body he showed, depends on the
size of the atoms the proximity OF those atoms and
in contact bur were balanced in their places by
traction and repulson. Heat tends to increase the
repulsve force. t1@
Specific gravity means the weight of body rela-
tiroiy to something else, the standard being water
1t was first used by Archimedes and is now practi-
cally determined by weighing the body in water and
out Of water, and subtracting one result from the
other
Two metals of different specific quantities melted
together have not great specific gravity be-
fore, because the ultimate particles of be-
tween those of the other. Brass, for instance, has
not as great specific gravity as the metals Of which
gold ID, mercury l3i and coppers.
Water and liquids are generally but little compress
sible indeed 1t was long thought to be incompressi
bic, but an instrument invented BY Capt. Ericsson,
deserts from the American publc,) shows very sat
isfactorily the compressbility of water
Gas changes It's state on being compressed and
becomes solid, which is the case with Carbonic Acid
Gas. Hardness does not depend upon the weight Of
a body; diamond which is the hardest known sub
stance Is not so heavy gold; sheet of paper may
be revoved SO fast as TO cut bar of soe and tai
low candle has been shot from gun through hall
perine, and in this the Chinese have the advantage
ofus their steel being very hard and not brittle as
ours,
Elasticity Is the power Of body to resume Its
original shape after compression or extension, but
does not depend upon the extent to which 1t may be
stretched thus glass more elastic than india rubber
Brhaeness is that state In which the cohesion OF
The particles is confined to short distances as with
glass, steel EAST iron, &c.
AIaUeubahyisa state in which the attraction be.
tween the particles is equal in all directions. Gold
may be beaten SO thin that 1900 leaves win make
only the thickness Of Il sheet Of ordinary writing
paper. #+ E
Ductaay ls the capaby of metal 10 be drawn
into wire Il L often confused with Availability
which Is the capability Of being hammered out into
a sheet. Gold which Is the most malleable Is the
least ductile metal Glass has great ductlity, and
may be drawn into fine thread.
1sndcity is the cohesion among the particles of a
mass.
Laeria is the last and mos, important branch Of
our subject and may be defined 10 be the stubborn
ness Of body TO stop when In notion or to be put
In motion when at reat. Force Is required In either
case. Persons jumping from wagon or car while
in motion thrown upon their face, because their
bodies have the velocity OF the car and the friction
OF the ground stops their feet while the body goes on
and falls
In sea sickness the heaying of the vessel gives the
blood more rapid circulation and motion than the
body and produces nausea, card placed on the
thumb with n csin over Il, the card may be knocked
om under leaving the coin in Its place, the inertia
Of the coin not being overcome nj the same time
Circus riders in going rapidly have tho same motion
as the horse, and when they leap through hoops &C.,
require no more eXertion than simple jump, when
the body goes on with the same speed as the horse
and he alighis upon him again without difficulty.
Motion Is only understood as compared with
something else. The furniture OF chr or boat Is rel
atively at rest and so with every thing upon the
globe, which is itself rapidly In motion.