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gasoline motor developing eight horse…power； and coupled direct
to a 2…kilo watt alternator。 At one end of the shaft of the
latter the disk discharger is mounted； its function being to
break up the train of waves into groups of waves； so as to impart
a musical sound to the note produced in the receiver。 A flexible
cable transmits the electric current from the generator to the
wagon containing the instruments。 The aerial is built up of
masts carried in sections。
The Germans employ a mobile apparatus which is very similar； but
in this instance the mast is telescopic。 When closed it occupies
but little space。 By turning the winch handle the mast is
extended； and can be carried to any height up to a maximum of
about 100 feet。 The capacity of these mobile stations varies
within wide limits； the range of the largest and most powerful
installations being about 200 miles。 The disadvantage of these
systems； however； is that they are condemned to territories where
the ground at the utmost is gently undulating； and where there
are roads on which four…wheeled vehicles can travel。
For operation in hilly districts； where only trails are to be
found； the Marconi Company； has perfected what may be described
as 〃pack〃 and 〃knapsack〃 installations respectively。 In the
first named the whole of the installation is mounted upon the
backs of four horses。 The first carries the generator set； the
second the transmitting instruments； the third the receiving
equipment； and the fourth the detachable mast and stays。
The generator is carried upon the horse's saddle； and is fitted
with a pair of legs on each side。 On one side of the saddle is
mounted a small highspeed explosion motor； while on the opposite
side； in axial alignment with the motor； is a small dynamo。 When
it is desired to erect the installation the saddle carrying this
set is removed from the horse's back and placed upon the ground；
the legs acting as the support。 A length of shaft is then
slipped into sockets at the inner ends of the motor and dynamo
shafts respectively； thus coupling them directly； while the
current is transmitted through a short length of flexible cable
to the instruments。 The mast itself is made in lengths of about
four feet； which are slipped together in the manner of the
sections of a fishing rod； and erected； being supported by means
of wire guys。 In this manner an antenna from 40 to 50 feet in
height may be obtained。
The feature of this set is its compactness； the equal division of
the sections of the installation； and the celerity with which the
station may be set up and dismantled in extremely mountainous
country such as the Vosges； where it is even difficult for a
pack…horse to climb to commanding or suitable positions； there is
still another set which has been perfected by the Marconi
Company。 This is the 〃knapsack〃 set； in which the whole of the
installation； necessarily light； small； and compact； is divided
among four men； and carried in the manner of knapsacks upon their
backs。 Although necessarily of limited radius； such an
installation is adequate for communication within the restricted
range of air…craft。
Greater difficulties have to be overcome in the mounting of a
wireless installation upon a dirigible。 When the Zeppelin was
finally accepted by the German Government； the military
authorities emphasised the great part which wireless telegraphy
was destined to play in connection with such craft。 But have
these anticipations been fulfilled？ By no means； as a little
reflection will suffice to prove。
In the first place； a wireless outfit is about the most dangerous
piece of equipment which could be carried by such a craft as the
Zeppelin unless it is exceptionally well protected。 As is well
known the rigidity of this type of airship is dependent upon a
large and complicated network of aluminium； which constitutes the
frame。 Such a huge mass of metal constitutes an excellent
collector of electricity from the atmosphere； it becomes charged
to the maximum with electricity。
In this manner a formidable contributory source of danger to the
airship is formed。 In fact； this was the reason why 〃Z…IV〃
vanished suddenly in smoke and flame upon falling foul of the
branches of trees during its descent。 At the time the Zeppelin
was a highly charged electrical machine or battery as it were；
insulated by the surrounding air。 Directly the airship touched
the trees a short circuit was established； and the resultant
spark sufficed to fire the gas； which is continuously exuding
from the gas bags。
After this accident minute calculations were made and it was
ascertained that a potential difference of no less than 100；00
volts existed between the framework of the dirigible and the
trees。 This tension sufficed to produce a spark 4 inches in
length。 It is not surprising that the establishment of the
electric equilibrium by contact with the trees； which produced
such a spark should fire the hydrogen inflation charge。 In fact
the heat generated was so intense that the aluminium metallic
framework was fused。 The measurements which were made proved
that the gas was consumed within 15 seconds and the envelope
destroyed within 20 seconds。
As a result of this disaster endeavours were made to persuade
Count Zeppelin to abandon the use of aluminium for the framework
of his balloon but they were fruitless； a result no doubt due to
the fact that the inventor of the airship of this name has but a
superficial knowledge of the various sciences which bear upon
aeronautics； and fully illustrates the truth of the old adage
that 〃a little learning is a dangerous thing。〃 Count Zeppelin
continues to work upon his original lines； but the danger of his
system of construction was not lost upon another German
investigator； Professor Schiitte； who forthwith embarked upon the
construction of another rigid system； similar to that of
Zeppelin； at Lanz。 In this vessel aluminium was completely
abandoned in favour of a framework of ash and poplar。
The fact that the aluminium constituted a dangerous collector of
electricity rendered the installation of wireless upon the
Zeppelin not only perilous but difficult。 Very serious
disturbances of an electrical nature were set up； with the result
that wireless communication between the travelling dirigible and
the ground below was rendered extremely uncertain。 In fact； it
has never yet been possible to communicate over distances
exceeding about 150 miles。 Apart from this defect； the danger of
operating the wireless is obvious； and it is generally believed
in technical circles that the majority of the Zeppelin disasters
from fire have been directly attributable to this； especially
those disasters which have occurred when the vessel has suddenly
exploded before coming into contact with terrestrial
obstructions。
In the later vessels of this type the wireless installat