130 
POPULAR SCIENCE NEWS. 
[September, 1890. 
with the other pole. In fact, it is not neces- 
sary to connect the lamp with the coil at all. 
Simply attaching it to a glass rod or other 
insulated handle and bringing it near the pole 
(Fig. 3) will develop considerable light. 
The experiment may be also varied as in 
Fig. 5, where the lamp is suspended by 
a wire, and an insulated metallic point 
connected with the induction coil brought 
near to it, when the lamp is both attracted 
and excited into luminosity. Numerous other 
variations of the experiment will suggest 
themselves. 
The small incandescent lamps of one or 
two candle-power are best adapted for these 
experiments,, unless the induction coil is 
of unusual size ; and it is hardly necessary 
to warn those accustomed to the handling 
of such coils that the wires conveying the 
secondary current should never be touched 
directly with the hands, or unpleasant, or 
even dangerous shocks may be felt. A glass 
rod, or some other good non-conductor, forms 
a convenient handle, around which the wires 
may be twisted. 
)♦> 
LIQUID GASES. 
The word gas was coined by the alche- 
mists, and is proba- 
only been well understood during the present 
century. Atmospheric air being everywhere 
present, was, of course, recognized from the 
earliest times ; and, although the early chem- 
ists soon discovered other forms of gaseous 
matter, they did not thoroughly understand 
them, and their terms fixed air, dephlogisti- 
cated air, etc., showed their inclination to 
consider them as varieties of the most familiar 
form. 
The distinction between a gas and a vapor 
is not a well marked one. A gas is a form 
of matter which retains the gaseous form at 
ordinary temperatures and pressure ; while a 
vapor is formed at a higher temperature or 
lower pressure, from a usually liquid or solid 
substance. Oxygen, for instance, is a true 
gas ; while steam, although resembling a gas 
in every way, is. formed from water at high 
temperatures, and when the temperature falls 
is condensed back into water again. 
Faraday first showed that many so-called 
permanent gases could be changed to liquids, 
or even solids, by cold and pressure. By 
generating chlorine in a closed glass tube, he 
easily succeeded in changing it to a yellowish 
liquid, which, when the pressure was re- 
moved, returned at once to the gaseous state. 
bly from the Ger- 
man£-ei'st., or ghost, 
showing the super- 
stitious ideas which 
they connected with 
this mysterious 
form of matter. In 
a gas the molecules, 
or ultimate pai ti- 
des of matter, are 
at such a distance 
from each other 
that there is no 
mutual attraction 
between them, and 
each separate parti- 
cle is free to move 
in any direction 
that external or 
inherent forces may 
impel it. 
It may be asked 
how we know that 
the molecules of 
gas are separated 
from each other, and why the 
of which they are composed may .not 
be absolutely continuous. The simplest 
answer to this question is found in the 
fact that gases chatige their volume under 
varying conditions of pressure. A gas can 
be squeezed together, as it were, and, as 
we cannot conceive of the possibility of doing 
this with an absolutely continuous mass of 
matter, it must, therefore, be made up of sepa- 
rate particles. 
Qf)^^^-''^! 
The nature and properties of gases have 
matter ( Sulphurous acid, the gas formed by burning 
sulphur, although gaseous at the usual tem- 
peratures, is changed to a liquid at a temper- 
ature of about 0° F. without any increase 
of pressure ; while carbonic dioxide requires 
a pressure of over 500 pounds to the square 
inch at a temperature of 32° before it will 
assume the liquid form. 
Up to within a few years, certain gases — 
such as oxygen, nitrogen, and hydrogen — had 
never been liquefied, and it was supposed that 
it was impossible to do so with any amount 
of cold or pressure that could be produced. 
By the aid of powerful apparatus, however, 
invented by Cailletet and Pictet, by which a 
temperature of over 200 degrees below zero, 
and pressures exceeding two tons to the 
square inch, were produced, oxygen, and 
finally all other gases, were liquefied, car- 
bonic oxide being the most refractory one. 
When ammonia gas is exposed to a tem- 
perature of — 40° at the ordinary pressure 
of the air, or to a pressure of about 100 
pounds to the square inch at the ordinary 
temperature, it is readily condensed to a 
liquid. When the pressure is removed, it 
returns to the gaseous state, and in so doing 
it absorbs a great deal of heat from the air or 
surrounding objects, quickly reducing their 
temperature many degrees below the freezing- 
point of water. This property is utilized in 
the artificial ice machines, in which liquefied 
ammonia is allowed to resume the gaseous 
condition in coils of pipe placed in a tank 
of strong brine in which cans of pure water 
are placed. The temperature of the brine is 
reduced far below the freezing-point of the 
water in the cans, which is soon transformed 
into a solid block of ice. The short ice crop 
of the past winter has led to the use of so 
many artificial ice 
machines that the 
price of ammonia 
has materially' risen 
i n consequence, 
and, unless the 
temperature of the 
ensuing cold season 
more nearly ap' 
proaches the aver- 
age, the demand 
for this most useful 
substance will be 
greater than ever. 
Posting Flowers. 
—To send flower buds 
by post, cut a potato 
into two pieces, bore 
lioles into them, and 
insert tlie stems of tlie 
buds, with cotton to 
support them. There 
is sufficient moisture 
in a good-sized potato 
to support a flower for 
two weeks in a moder- 
ately cool tempera- 
ture. Flowers from bouquets or baskets may be 
preserved in the same way. The potatoes can be 
hidden by leaves or moss. 
Crushed Steel is said to be coming into use for 
cutting stone. It appears to be made by quenching 
very high-carbon steel in cold water from an exces- 
sively high temperature, such as would over-heat 
steel for most purposes. This renders it not only 
hard, but rather brittle, so that it is possible to pul- 
verize it. It is crushed in a stamp-mill, and sifted 
closely to size. It is said to be not only cheaper 
but much more effective than emery, giving a better 
and quicker polish, and lasting much longer. 
