The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1881-01-22
Tnpromptu Ingenuity.

DOme years dSo, OPahlon eto1n0I,
while crossing the Bay of Biscay in Sc
we're storm, gave such indications, by an
unusual noise at the stern, that there was
something wrong with the screw propeller
or its shaft outside of the ship-that is, in
the open space between the stern and rud-
der posts where the screw revolves. There
was no dry dock in any of the ports on the
coast where the ship could go to be exam
ined and on arrival at Vigo it appeared
as if there was no alternative but to re-
move the cargo from the stern, and by
placing it forward thus lift the screw pro-
peller and shaft to the surface of the wa
ter The alternative, simple as it was,
meant serious delay and great expense.
Before commencing to remove the cargo,
another consultation was held. 1t was
then decided to put the stern of the ship
over bed of light colored sand ; and as
tn water was very clear, there might be a
possibility of ascertaining the extent or
cause of the mishap. For two days after
the vessel was so placed, the wind caused
ripple on the water, which effectually
prevented anything being seen. 1t was
then suggested by some one on board to
try the use of oil on the surface of the
water round the stern of the ship. The
effect was most satisfactory. The water
was becalmed as if by magic, and it was
then seen that the wedge or key which
keeps the propeller in its place on the shaft
had come partly out, and thus left the
screw loose on the shaft, which caused the
noise. By continuing the use of oil for
few hours the wedge was ultimately driven
into it's place and secured. Many days of
detention and the use Of costly appliances
and labor were thus saved.
A few years ago an iron bridge of con-
siderable length, the weight being about
two hundred tons, was constructed in Eng
land, and erected in remote part of Ger
many. By some mishap, the bridge, when
finished, was found to be some distance
''out" to one side, an error which the pro-
prietors insisted should be rectifed. To
take down and e-erect the bridge would
be simply ruin to the contractor. But ne
cessity is the mother of invention, and so
it proved in this case. 1t was summer
time, and the contractor proceeded to find
the amount Of expansion which was caused
by the heat of the sun over the whole
length of the bridge. He next ascertain
ed what contraction took place in the
night by cooling. Armed with these data
he thought it might be possible to bring
the bridge TO its proper position in few
days. The bridge, of course, in its ordi
nary condition, expanded from the center,
pushing its two ends outward, or farther
apart, and again contracting toward the
center Taking advantage Of these condi
tions, one end was made fast in the morn
ing, and the bridge was forced to expand
from that immovable point, instead of
from the middle, as formerly. When the
iron composing tie bridge had expanded
to its full extent in the direction intended,
that end was released, and the opposite end
made fast The bridge then contracted
toward it's true position. Thus, whatever
was gained by the days expansion was Sc
cured by the subsequent contraction when
the metal cooled at night, and the process
being renewed day by day, the work was
successfully accomplished.
An ingenious application of expansion
and contraction in metals was made use of
in France, and has frequently been taken
advantage of since. The walls of large
building in Paris were observed to be Civ
ing way by bulging outwards, and the
problem was to bring them back to their
vertical position. For this purpose num-
ber of bars of iron having screws and nuts
on each end were let through the opposite
walls and across the intervening space be-
tween them The nuts and screwed por-
ton of the bars were outside. The bars
were now heated by number of lamps
suspended below them until they had ex-
panded as much as possible, and the nuts
screwed up against the outsides of the two
opposite walls. The lamps were next re-
moved, when the heated bars, in cooling,
gradually contracted in their length, bring
ing the walls very gently, but with ire
sistibe force, into their normal position.
1t is we'll known that in working iron,
such as Welding two pieces together, and
even in its manufacture, hollow places or
flaws occur, with merely an outside skin
over the defective parts, which any test
but destructive one would fail to discov
er. Nor would it be difficult to point out
numerous examples of disaster thus occur
ring. To test the homogenity Of the
metal, bar of iron is placed on the equa
torial line. A compass with very seusi-
tive needle is passed along in front of the
bar, the needle of course pointing at a
right angle to it. If the bar is perfectly
solid through its whole length, the needle
will remain steady. If, however, there
should be flaw or hollow place in the bar
the needle will be DETECTED as it passes
from the solid to the hollow place, back
,oard toward the solid iron passing on
over the hollow place, the needle will come
within the range of the solid iron at the
other end of the flaw, and will again be
DETECTED foy1cayd. IF the bar be cut