180 
WIRELESS TELEGRAPHY. 
another little point which goes to prove that resonance does not come 
in. It is found that the Righi apparatus, which has hitherto been con¬ 
sidered the best form of radiator for moderate distances, presents no 
particular advantage when connected to a long vertical wire. With 
sufficient energy at command it is only necessary to fix small spheres 
on the discharging rods of the coil, for practically the radiator in this 
case consists primarily if not solely of the vertical wire. There is, 
however, one exception to this rule. If a capacity consisting of several 
square feet of plate copper be fixed at the upper ends of the vertical 
conductor, tuning becomes more effective, and to obtain the best results 
regard must be paid to this. 
There is another point of considerable interest. Although it is 
necessary to have the earth connected to the radiator to obtain the 
best results, yet when the receiving apparatus is adjusted to record 
good signals, the disconnection of the earth and the substitution of a 
capacity consisting of a couple of feet of brass strips an inch wide suf¬ 
ficed to maintain communication. In other words the earth is almost 
unnecessary for receiving, and the electrical surging takes place 
simply from the vertical wire on one side through the coherer to the 
capacity on the other side. 
Reference has been made to lightning. That is a point that re¬ 
quires considerable care when making experiments with very long 
wires. If you erect and insulate a vertical wire in ordinary fine 
weather and let it remain idle for a few seconds it accumulates a charge 
which is quite sufficient to give you a sharp prick when you touch it, 
and which is sufficient to actuate the coherer so that when atmospheric 
disturbances are rife, false signals are frequently received. It would 
always be wise in using very long wires to put a shunt of somewhat 
high resistance and self induction between the receiving wire and the 
earth so that it may carry off all disturbing charges. By disturbing 
charges I mean minor ones that would be likely to interfere with the 
reception of signals, because inductive lightning effects would pro¬ 
bably pass through the shunt coil to earth, whereas the rapid oscilla¬ 
tions due to induction would pass through the coherer. For heavy 
discharges, however, further precautions are needed, and it would be 
wise whenever using lofty conductors to provide a good lightning pro¬ 
tector of the type used for telegraph instruments. 
By the way, in connection with the question of the law of distance I 
should perhaps have pointed out that this law does not hold good over an 
indefinite distance. This is due to various causes. The extra distributed 
capacity of a very long wire must materially slow down the rate of oscilla¬ 
tion. Again the rotundity of the earth cuts down the useful length of the 
conductor whilst probably reflection and absorption come into play, but 
it is without question that the law would not hold good, say for 30 or 
40 miles. In connection with certain experiments made by Mr. Mar¬ 
coni, aided by Captain Kennedy, between Salisbury plain and Bath, a 
distance of some 40 miles, they raised wires into the air by means of 
kites to a height variously estimated as between 800 feet and 800 
yards. Even if it had been only 800 feet that ought to have sufficed 
