The Middlebury register and Addison County journal. [volume] (Middlebury, Vt.) 1883-1885, 1885-10-30
SCIENTIFIC AND INDUSTRIAL

Iron bars and steel are elongated by
magnetization, the latter not so much,
but nickel bars are shortened.
Round chimneys are best for work
shops, factories, etc. They deliver the
smoke more easily and are less exposed
to the wind. They are not, however, so
easy to build,
Professor Tyndall has stated that the
purcst water he ever obtained was from
melted block of pure ice. The water
of the chalk districts of England he con.
siders remarkably pure.
NJ. Fordoz gives very simple and use
full method for detecting lead in the lin
Ing of culinary utensils. The vessel
being carefully cleaned to remove grease,
drop of nitric acid is applied to any
part, and a gentle heat is used to dry the
spot. A drop of solution of iodide of
potassium is applied to the spot; and, if
lead be present, a yellow ioddc of lead
is formed.
Stove polish is made from plumbaro,
some of the richest mines of which are in
Guaymas, Mexico. The plumbago comes
from the mines in sacks weighing 100
pounds each. 1t is then crushed and
separated 10y the use of huge pans. the
coarse quality being seat through the
crusher again. and only the very fine
going into the bins tc be mixed with oils
and made into stove polish.
Admiral Mouchez has taken. at the
Paris observatory, a photograph of a
section of the sky some five degrees
square showing nearly 5000 stars on
plate ten inches square. The print
shows quite clearly stars of the four
tcenth magnitude; while on the mega
tive some even of the fifteenth magni-
tude appear which, however, could not
be transferred to the paper. The plate
is perfect all over, manifesting no weak
ness even mt the extreme edge. If these
twenty-five square degrees may be taken
as representative portion of the sky,
the numbers of stars visible to the four
tecnth magnitude inclusive, is some
thing over 20, 900, 900.
A new method of preserving fruit is
practiced in England. Pears, apples,
and other fruits are reduced to paste,
which is then pressed into cakes and
gently dried. When required for use it
is only necessary to pour four times their
weight OF boiling water over them, and
allow them to soak for twenty minutes,
and then add sugar to suit the taste. The
fine flavor of the fruit is sad to be re-
tanned to perfection. The cost of the
prepared product is scarcely greater
than that of the original fruit, differing
with the supply and price of the latter;
the keeping qualities are excellent. so
that it may be had at any time of the /
year, and bears long sea voyages with |
out detriment. No peeing or coring
is required, so there is no waste.
Some interesting Instances of spontan-
eous ignition of various substances. with .
attendant losses of property, would APP ,
pear TO have been due to simple ignor- !
ance of the relations of animal, vegetable .
and mineral oils to combustion. Pro-
fcssor Altied points out that the former
are much safer than the latter,
since they do not ignite at low tempera-
lures nor give off vapor which, when
mixed with certain portion of air, ex-
podes in contact with flame; on the
other hand, in their liability to spontan-
eous ignition, when freely exposed to
the air, under certain conditions, they
possess dangerous property from which
the mineral oils are free. Then, too, the
animal and vegetable oils differ consid-
erably among themselves, in the
rate at which they cause the genera
ton of heat on being exposed to air, up
on the surface of fabrics, shavings or
other materials, though all are more or
less liable to this result when spread out
in thin films, or in any other state of
minute division. What are known as
drying oils are particularly susceptible
to such atmospheric Influences, the dry
ing itself consisting in the conversion of
the oil into kind of rosin by the action
Of the air.