Vol. XXV. No. 7.] 
POPULAR SCIENCE NEWS. 
97 
Iiundred and twenty-five revolutions per minute. 
Just over the fan was a tin flue about three feet 
square, into whicli the air was fanned. The fan 
is something lilce a water-wheel used by mills. 
The blades of tlie wheel catch the air and fan it 
with additional force into the flues. In the center 
of this room is a mass of steam-pipes, — some 108,- 
000 feet in all, — wliich generates the heat caught 
by the fan. But before passing into the fan it is 
.mixed with a current of cool, pure air, which 
pomes in through an opening in the other side of 
lie room which leads to a part of the tower eight 
Iteet square and one hundred and sixty-five feet 
?high. 'Ilius, by tlie combination of hot and cold 
air, tlie building is heated, and at the same time 
furnished with pure, fresh breathing air. In sum- 
. mer a fan of this kind placed near a window in 
the basement or in an open tower on the roof c^iu 
be used to circulate cool air throughout the build- 
ing. In many theatres a fan is set in the dome of 
the roof, and thus the air in the whole house is 
changed every five minutes. 
Fifty years ago all church organs were pumped 
by hand. XoW nearly all have the bellows filled 
with air generated by a fan run by steam, electric, 
or water motors. The bellows of the forge made 
famous by Longfellow in his poem, "TTie Village 
lUacksmith," was "blowed" by hand. Now, in 
large shops where motor power of some kind is 
handy, a fan can be run which forms a blast. ITie 
workman, instead of "blowing" the fire, turns 
on the blast by opening a valve in the pipe. Plan- 
iiig-mills use a device of this kind to blow the 
sawdust and dirt ofl" the machines. In foundries 
a Idast is used to form a draft to kindle the fire. 
A description of the manner in which iron is 
melted may be interesting. A layer of coke is 
first placed in the huge cauldron, and then pig 
iion and coke alternately, llie intense heat gen- 
1 rated by the blast burns the coke so fine that it 
collects on top and is easily pushed aside. The 
iron is then let out into small "pourers"' as 
needed. 
It seems almost incredible that air when com- 
pressed can be used to lift immense weights, press 
tlie sand in molds in foundries, and" do other work 
formerly done by hand. The air is compressed by 
:ia engine made for that purpose. 'J'he air is let 
into the cylinder by a valve in a pipe. ITie instant 
the cylinder is full of air the valve closes and does 
not let in any more air until the supply already in 
is compressed and disposed of. When the engine 
reverses, the air is forced out through a valve into 
a tank by the piston Iiead in the cylinder. When 
tlie supply of air is exhausted, the valve is closed 
automatically until the next lot is compressed. 
Air thus handled will stand about eighty pounds 
pressure to the cubic inch. Small pipes lead from 
this tank all over the shops, where it is used for 
sundry purposes— blowing dirt oft' of machines, 
testing cylinders, etc. To do the lifting spoken 
of, small air engines are fixed in an upright posi- 
tion on cranes, and are made to run a chain at- 
tached to a pulley block, thus lifting or lowering 
anything as the case demands. 
Another contrivance much used is a cylinder 
attached to a truck which runs along a track 
overhead. The air raises the piston and lifts up 
any « eiglit attached to the hook on the lower end 
of the piston rod. 'Hie largest object I ever saw 
lifted weighed 13,800 pounds, actual weight. 
These cylinders are especially adapted for use in 
niachiue-sliops, where they can be readily placed 
over large machines or in any place where heavy 
lifting is required. One man alone can do more 
with the pneumatic crane than a dozen men could 
formerly do with chain and pulley. It will proba- 
bly not be long before we hear of some other de- 
vices in which air plays an active part, for its 
adaptability to compression renders it a valuable 
aid to mankind. 
AN ANCIENT IRRIGATING MACHINE. 
In a recent number of the Scientific American is 
described a primitive but ingenious machine for 
elevating water for purposes of irrigation, which 
has been in use in India for many centuries. As 
shown in the engraving, it consists of a double 
system of troughs, or water-conductors, arranged 
in a zigzag manner, and mounted on a horizontal 
axis so that the whole forms a great pendulum, 
which is set in motion by ropes held in the hands 
of two men standing on opposite banks of the 
stream. At each angle or point where two troughs 
come together, is placed a movable piece of board 
which acts as a valve and prevents the water from 
flowing back again. It will be seen that, as the 
machine is swung to and fro, the end of each con- 
ductor dips under the water alternately, scooijing 
up a certain quantity, which at each subsequent 
movement passes by its own weight into the 
trough above, until it is finally discharged at the 
top into a gutter which conveys it over the land 
to be irrigated. 
This device, although clumsy and uneconomical, 
serves its puri)ose fairly well, especially in a land 
where human labor is of but little value, and is 
of interest as showing considerable originality 
and knowledge of the elementary piinciples of 
hydraulics on the part of its ancient and unknown 
inventor. 
^ ♦♦♦ 
[Original In Popdlak Science News.] 
CHLORINE. 
BY GEOKOK I,. liUUDITT. 
Chlorine, one of the most abundant of the ele- 
ments, is the most important member of the halo- 
gen group. The other members of the group are 
bromine, iodine, and fluorine. Their characteristic 
features are their indifl'erence to one another, and 
their affinity for the metals with which the}' unite 
to form a class of salts. 
Chlorine (CI.;, 35.5) was discovered by Scheele 
in 1774, but it was first recognized as an element 
by Davy in 1810. It never occurs fi-eo in Nature, 
but exists in large quantities in combination with 
sodium, potassium, calcium, magnesium, and other 
elements. Sodium chloride (Na CI) is the prin- 
cipal source. It is also made by the following 
reaction : 411 CI 4- Mn Oj = Mn Cl^ -|- Cl.^ -f- 2Hj O. 
The chlorine thus produced is a green or green- 
ish yellow gas, with a powerful, suffocating odor. 
If breathed in small quantities it produces irrita- 
tion of the air passages and coughing. Chlorine 
is soluble in about one-half of its bulk of cold 
water, and the solution which is readily formed 
by shaking the water and the gas together has the 
odor, color, and taste of the gas. In consequence 
of this solubility it cannot be conveniently col- 
lected over water. The common method is to 
collect it in dry bottles by downward displace- 
ment. Cldorine is not combustible, although it 
sometimes supports combustion. Many bodies 
burn readily in it, as is shown in the case of cop- 
per leaf, finely divided antimony, and arsenic. 
Chlorine is valuable as a disinfectant, a bleaching 
agent, and an oxidizing agent. Its strong attrac- 
tion for hydrogen causes it to decompose water 
and set free oxygen which may unite with some- 
thing else. 
Chlorine coml)ines with all non-metallic ele- 
ments, forming an important class of compounds, 
called chlorides, all of which— with the exception 
of argentic chloride, cuprous and mercurous chlo- 
rides — are more or less soluble iu water. To test 
a solution for a chloride, add argentic nitrate. If 
a chloride is present, a white precipitate will be 
formed. This is argentic chloride, which is insol- 
uble. The commonest chloride we meet with is 
chloride of sodium (Na CI), or common salt, the 
properties of which are well known. The blow- 
pipe test for a chloride is as follows : Make a 
borax bead and add oxide of copper ; then add the 
substance to be tested. If it is a chloride, a beau- 
tiful bluish green flame will be given. 
The most important combination of chlorine 
with the non-metallic elements is its combination 
with hydrogen to form hydrochloiic acid (II CI). 
Equal volumes of hydrogen and chlorine may be 
mixed together in a vessel, and no action will take 
place while the vessel is kept in the dark. Rut as 
soon as it is exposed to direct sunlight, a loud 
explosion takes place. The gases unite, forming 
a colorless but strongly acid gas — hydrochloric 
acid gas. It fumes strongly when exposed to the 
air. A solution of this gas in water makes hydro- 
chloric acid. The gas is very soluble, water dis- 
solving about 450 times its own volume of it. It 
is usually made from common salt : 2Na CI -|- 
11, SO.=Na H SO,-)-H Cl-f-Na Cl=Na, S04-I-2H CI. 
The acid is powerful and gives a strong acid re- 
action. It dissolves many metals, setting free 
hydi'ogen, and forms chlorides. The commercial 
hydrochloric acid, commonly called muriatic acid 
or spirit of salt, is generally yellow, owing to im- 
purities ; the pure acid is colorless. A little con- 
centrated Hj SO^ added to about three grammes of 
salt in a test-tube will generate enough of the gas 
to show its solubility and acid reaction. 
Chlorine gas is a great bleaching agent. This 
power depends upon the fact that chlorine has a 
greater affinity for hydrogen than for oxygen. 
If a dry piece of calico is suspended in a jar of 
chlorine gas, nothing will happen ; but if the cal- 
ico is taken out, moistened, and put back, it will 
be quickly bleached. The chlorine in the jar 
combines with the hydrogen of the water on the 
cloth, and decomposes the water. The oxygen, 
freed from its former combination, unites with 
the coloring matter on the calico and removes it, 
leaving a wliite cloth. Bleaehing-powder, Ca O 
Clj, is commonly used. It is frequently, but im- 
properly, called chloride of lime. When acted upon 
by an acid it gives chlorine. The cloth to be 
bleached is first immersed in a solution of bleaeh- 
ing-powder, and then dipped into dilute sulphuric 
