Evening star., 1896-08-22
lied is about equal to the power expended
in generation.
A Matter of Emc}encv

A Matter OF Emciency.
theoretically the total efficiency Is aot-
uaily greater. but it is a matter Of fact In
practical use 1t is slightly less It is, nev-
ertheless, true that in tests made on the
Hardie street car motor 1t has been found
possible to realize about 8 per cent moro
energy or work from given quantity of
coal by burning the coal in good type of
air-compressing apparatus and using this
air. under reheating. in the Hardie motor,
than as II the coal were put into an ordf-r
nary locomotive and used directly for the
paradox is due to the added power gained
from reheating the air.
comparing American and Partisan ap-
pliances again. the efficiency developed un-
ger the Popp system in Paris. with re-.
Eeatlng, Is stated at from 90 to 20 per cent,
Is per cent being given as the maximum.
Assuming loss Of from to 5 per cent un-
der the American method 1t follows that
tne degree OF efficiency realized under the
fopp system Is something more than 20
per cent less than that attained in this
country. 1t Is to be noted further that
compressed air began to be used in Paris
long before 1t was taken up in this country
the Mekarski system Of surface transit
alone having been in operation for more
than ten years.
With the perfection OF compressing ap-
paratus and the reheatng system, has
come a third important development, which
mas chiefly made possible the use of COM
vention Of what is known as the Names
mann tube for the storage Of the air. The
latter Is simply seamless tube or flask,
made Of mild steel of any desired size and
capable cf receiving and holding air charged
to very high pressure. Up to the time Of
its Introduction it had been practically
impossible to provide suitable reservoir
or holder. Those which were employed
were enormously heavy, took up a wholly
impracticable amount OF space, very often
exploded and always leaked. The loss in
one way or another was very great. The
Mannesmann tube solved the problem by
providing chest that was practically air
tight. that IL 1t burst did not fly in pieces
but simply ripped as would a leather bag.
and was therefore not a hazard to life; it
was light and it took up very little space.
High Charge.
These tubes are now made to carry al
most any charge of air. In the case Of the
Hardie motor their testing strength is 1000
| pounds per square inch and their maximum
charge about 1900 pounds. These steel
cylinders are distributed underneath the
| seats and under the car body in such a way
| as not to infringe upon the room Of an Or
| dinary steet car, and hold fifty-one cubic
| feet Of air. sufficient to run the fifteen
| or eighteen miles. For the reader appre-
| hensive Of sitting over so highly charged
device. it may be stated that the whole
| effect of an explosion of one of these tubes
| would be loud report rush of air and a
slight disturbance of the atmosphere i'm
| medately adjacent. There would be no
| flying pieces of pipe, no steam or hot air
to scald and all you would see afterward
| would be an ugly rent In the tube.
Such is the rough outline of the impor-
| tant elements of the advance in the art.
| The improvement in the devices for COM
] preston represented economy of produc-
| ton, the development of the reheating pro-
| OF power derived from the air, and in conse-
Quence a still further cheap ening, while
| the seamless tube offered at once safety
storage and insurance from loss.
By virtue of these improvements the re-
| duction in the cost of manufacture has been
very great. AS computed by Compressed
Air. to the editor of which I am indebted
| for much Information, air may now be
compressed to high pressures for consider
| ably less than cents per 1000 cubic feet
1t Is probable that air could be compress
ed piped through large city and sold at
profit for cents
1t is to this cheapening, not less than to
its mobility and the ease with which ii may
be applied, that the wide use of compressed
air at the present time is due. Once cheap
power offered, it thereafter remained
but to develop the various special devices
and appliances by which 1t could be utilized.
One after another these inventions have
been made. until it is now estimated that
this wonderful force is employed for some
thing more than 200 distinct purposes.
Future Of the Force.
When we consider the probable future Of
the new force, as such it may fairly be
called, we live over again our experience
with its rival, electricity. The immediate
conclusion, after survey Of the sufficiently
marvellous things that 1t can and actually
does do. Is that there is hardly limit to be
set to Its possibilities. But brief calcula-
ton will define its limits with some ac-
curacy. To compress a given quantity Of
air requires given amount of power. and
the result to be realized in work cannot be
greater than the amount of power employed
in generation. Otherwise you have per-
petual motion-a proposition that is not
patentable, and is otherwise open to sus-
picion. 1t follows with reasonable degree
of cogency that compressed air will not be
utilized save where. by reason of greater
utility or convenience 1t Is economy to con-
vert your original power into this form of
potential energy. 1t is not probable that
compressed air will be used to run railway
trains or steamships. although 1t is con-
ceivable that it might be valuable in days
to come when We shall fly through the
heavens.
But, on the other hand. compressed air Is
superior to steam piping or any form Of
shafting for the conveyance of power A
long series OF tests at the Pullman shops
near Chicago have demonstrated the i'm
mense economy which lies in its use and 1t
will. therefore. be universally introduced at
these works. as 1t is in many other great
car shops. as in Jersey City, Topeka, Omaha
ana elsewhere.
BY far the largest use. however, will come
when compressed air is manufactured in
huge central stations. similar to that of
the Popp system in Paris and Is distributed
in mains and sold commercially. just as are
gas and water and electricity. Then hardly
limit may be set to its usefulness 1t will
be in every home. as in every office Every
house will have its elevator, by which. with
the turn of your hand, you may lift yourself
from floor to floor. The housewife will
sweep and dust with air, and 1 do not doubt
that in time, madam. it will come to wash
your dishes and smash your choicest china
ware with all the dexterity, If not with the
same sangfroid of your most Accomplished
handmatden. 1t may supply fresh and cool
ing air in the summer time to the over
heated offices, the factory or the sleeping
room. The time may come when 1t will
whisk letter from New York to San Fran
cisco between the opening and the closing
Of the business day. What else it NAV do is
probably wrapped In the brain of the seedy
and neglected gentleman of invention and
applied science.
INCANDESCENT LIGHTS.