EFFECTS OF EXPANSION.
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cannon Dali, when heated, cannot be
made 10 enter an opening, through which,
when cold, it passes rapidly. glass
stopper sticking fast in tho neck Of bot.
tie, may he released by surrounding the
neck with cloth taken out OF warm wa
Ter, or hy immersirg the bottle in the wa
ter up 10 the neck: the binding ring is
thus heated and expanded sooner than
the stopper, and so become slack or loose
upon it. Pipes for conveying hot water,
steam, hot air, &c. if Of considerable
length, must have jennings that allow
degree oc shortening and lcng.hening.
otherwise change Of temperature may
destroy them. An incompetent person
undertook to warm large mandatory
by steam, from one boiler. He laid a
rigid main pipe along passage, and OPEN
ed lateral branches through holes into the
several apartments. but on his first ad-
mi,ting tho steam, the expansion Of the
main pipe tore it away from all its
branches. In on iron railing gate
which during cold day may be loose
and easily shut or opened in warm day
may stick, owing TO there being greater
expansion Of it and Of The neighboring
railing, than Of the earth on which they
are placed Thus also the centre Of the
arch Of an iron bridge is higher in warm
than in cold weather: while on the con-
trarv, in a supcnsion or chain bridge the
centre is lowered. The iron pillars now
SO much used to support the from. walls Of
houses, Of which the ground stories serve
as shops with spacious windows, in warm
weather really lift up the wall which rests
upon them. and in cold weather allow it
again to sink or subside in degree con-
siderably greater than il the wall were
brick from top to bottom. The pitch Of a
piano forte is lowered in warn, day. or
in warm room, owing to the expansion
Of the strings being greater than the
wooden framework; and in cold the re-
verse will happen. harp or piano,
which is we'll tuned in a morning draw
ing woom, cannot be pcrle city in tune
when The crowded evening party has
heated the room. Bell wires, too slack
in summer, may be Of the proper length
in winter. There exists most extraor-
dinary exception, already mentioned, TO
the law Of expansion by heat and con-
traction by cold. producing unspeakable
benefits IN nature, namely, in the case OF
water. Water contracts according to the
law only down to the temperature Of forty
degrees, while, from that to thrty-two
degrees. which is its freezing point, it


gain d,lates. Avery curious consequence
of this popularity is exhibited in the wells
Of the glaciers Of Switzerland and else


where, that when once pool or shallow
we'll on the ice commences 1t goes on
quickly deepening itself until it penetrates
TO the earth beneath. Surprising the sur
face Of the water originally to have near


ly the temperature Of the melting ice. or
thiny-two degrees, but to be afterwards
heated by the air and sun. instead Of the
water being thereby dilated or speciGcal-
| ly higher and detained at the surface, it
becomes heavier the more nearly it is
heated TO forty degrees, and therefore
sinks down TO the bottom Of the pit or
we'll; but there, by dissolving some Of
the ice, and being consequently cooled ii
is again rendered lighter, and rises TO be
heated as before, again to descend; and
this circulation and digging cannot cease
until the water has bored its way quite
hrough.-ArnoN.