While wonderful success has attended the development

of the dirigible (steerable) balloon the most ardent

advocates of this form of aerial navigation admit that it

has serious drawbacks. Some of these may be described

as follows:

Expense and Other Items.

Great Initial Expense.--The modern dirigible balloon

costs a fortune. The Zeppelin, for instance, costs more

$100,000 (these are official figures).

Expense of Inflation.--Gas evaporates rapidly, and a

balloon must be re-inflated, or partially re-inflated, every

time it is used. The Zeppelin holds 460,000 cubic feet

of gas which, even at $1 per thousand, would cost $460.

Difficulty of Obtaining Gas.--If a balloon suddenly

becomes deflated, by accident or atmospheric conditions,

far from a source of gas supply, it is practically worthless.

Gas must be piped to it, or the balloon carted to

the gas house--an expensive proceeding in either event.

Lack of Speed and Control.

Lack of Speed.--Under the most favorable conditions

the maximum speed of a balloon is 30 miles an hour.

Its great bulk makes the high speed attained by flying

machines impossible.

Difficulty of Control.--While the modern dirigible balloon is

readily handled in calm or light winds, its bulk

makes it difficult to control in heavy winds.

The Element of Danger.--Numerous balloons have

been destroyed by lightning and similar causes. One of

the largest of the Zeppelins was thus lost at Stuttgart

in 1908.

Some Balloon Performances.

It is only a matter of fairness to state that, under

favorable conditions, some very creditable records have

been made with modern balloons, viz:

November 23d, 1907, the French dirigible Patrie, travelled

187 miles in 6 hours and 45 minutes against a

light wind. This was a little over 28 miles an hour.

The Clement-Bayard, another French machine, sold

to the Russian government, made a trip of 125 miles at

a rate of 27 miles an hour.

Zeppelin No. 3, carrying eight passengers, and having

a total lifting capacity of 5,500 pounds of ballast in

addition to passengers, weight of equipment, etc., was

tested in October, 1906, and made 67 miles in 2 hours

and 17 minutes, about 30 miles an hour.

These are the best balloon trips on record, and show

forcefully the limitations of speed, the greatest being not

over 30 miles an hour.

Speed of Flying Machines.

Opposed to the balloon performances we have flying

machine trips (of authentic records) as follows:

Bleriot--monoplane--in 1908--52 miles an hour.

Delagrange--June 22, 1908--10 1/2 miles in 16 minutes,

approximately 42 miles an hour.

Wrights--October, 1905--the machine was then in its

infancy--24 miles in 38 minutes, approximately 44 miles

an hour. On December 31, 1908, the Wrights made 77

miles in 2 hours and 20 minutes.

Lambert, a pupil of the Wrights, and using a Wright

biplane, on October 18, 1909, covered 29.82 miles in 49

minutes and 39 seconds, being at the rate of 36 miles

an hour. This flight was made at a height of 1,312 feet.

Latham--October 21, 1909--made a short flight, about

11 minutes, in the teeth of a 40 mile gale, at Blackpool,

Eng. He used an Antoniette monoplane, and the official

report says: "This exhibition of nerve, daring and ability

is unparalled in the history of aviation."

Farman--October 20, 1909--was in the air for 1 hour,

32 min., 16 seconds, travelling 47 miles, 1,184 yards, a

duration record for England.

Paulhan--January 18, 1901--47 1/2 miles at the rate of

45 miles an hour, maintaining an altitude of from 1,000

to 2,000 feet.

Expense of Producing Gas.

Gas is indispensable in the operation of dirigible balloons,

and gas is expensive. Besides this it is not always

possible to obtain it in sufficient quantities even in large

cities, as the supply on hand is generally needed for

regular customers. Such as can be had is either water

or coal gas, neither of which is as efficient in lifting

power as hydrogen.

Hydrogen is the lightest and consequently the most

buoyant of all known gases. It is secured commercially

by treating zinc or iron with dilute sulphuric or

hydrochloric acid. The average cost may be safely placed

at $10 per 1,000 feet so that, to inflate a balloon of the

size of the Zeppelin, holding 460,000 cubic feet, would

cost $4,600.

Proportions of Materials Required.

In making hydrogen gas it is customary to allow 20

per cent for loss between the generation and the introduction

of the gas into the balloon. Thus, while the

formula calls for iron 28 times heavier than the weight

of the hydrogen required, and acid 49 times heavier, the

real quantities are 20 per cent greater. Hydrogen weighs

about 0.09 ounce to the cubic foot. Consequently if we

need say 450,000 cubic feet of gas we must have 2,531.25

pounds in weight. To produce this, allowing for the 20

percent loss, we must have 35 times its weight in iron,

or over 44 tons. Of acid it would take 60 times the

weight of the gas, or nearly 76 tons.

In Time of Emergency.

These figures are appalling, and under ordinary conditions

would be prohibitive, but there are times when

the balloon operator, unable to obtain water or coal gas,

must foot the bills. In military maneuvers, where the

field of operation is fixed, it is possible to furnish supplies

of hydrogen gas in portable cylinders, but on long

trips where sudden leakage or other cause makes descent

in an unexpected spot unavoidable, it becomes a question

of making your own hydrogen gas or deserting the balloon.

And when this occurs the balloonist is up against

another serious proposition--can he find the necessary

zinc or iron? Can he get the acid?

Balloons for Commercial Use.

Despite all this the balloon has its uses. If there is to

be such a thing as aerial navigation in a commercial

way--the carrying of freight and passengers--it will

come through the employment of such monster balloons

as Count Zeppelin is building. But even then the carrying

capacity must of necessity be limited. The latest

Zeppelin creation, a monster in size, is 450 feet long,

and 42 1/2 feet in diameter. The dimensions are such as

to make all other balloons look like pigmies; even many

ocean-going steamers are much smaller, and yet its passenger

capacity is very small. On its 36-hour flight in

May, 1909, the Zeppelin, carried only eight passengers.

The speed, however, was quite respectable, 850 miles

being covered in the 36 hours, a trifle over 23 miles an

hour. The reserve buoyancy, that is the total lifting

capacity aside from the weight of the airship and its

equipment, is estimated at three tons.