128 
WIRELESS TELEGRAPHY. 
have been made not only in this but in other countries, and we have 
now obtained somewhat definite views of the laws which govern this 
method of transmission. First dealing with vertical wires it has been 
demonstrated mechanically, and proved practically, that within cer¬ 
tain limits the product of the two heights bears a definite relation to 
the distance over which signals can be obtained. When transmission 
takes place over land by means of two vertical wires each 50 feet high, 
a range of one mile is attained, giving a product of 2500 as the square 
of 50. Within somewhat undefined limits the law of vertical heights 
holds good and is as follows :— 
h = 
*\f W X X 
Where 
n = 
Height in Feet 
x = 
No. of Miles 
h = 
Height Mercury 
To reach distance 
x :— 
Comparing these figures with the published results of the experi¬ 
ments across the British Channel together with others made over in¬ 
lets of the sea at Spezzia, it should be possible to signal a distance of 
one mile with wires about 35 to 40 feet in height. The discordance 
in the two classes of experiments is well marked, and we can only con¬ 
clude that there is a difference in the transmission of Hertzian waves 
over land and over water. During the course of some electro-mag¬ 
netic experiments in the Bristol Channel which were conducted in 
1892, we had absolute evidence that the waves were reflected from 
the surface of the water, and I cannot help thinking that reflection 
plays a very important part in the long distance experiments over seas 
and inlets which have been carried out in various places. 
Professor Slaby,who has made experiments in Germany, has observed 
the same difference in transmission over land and water, and he is re¬ 
ported to attribute this to the fact that the atmosphere over water is freer 
from dust particles than on land. With all deference to such an eminent 
authority I cannot quite accept this as a full explanation for two reasons : 
first, I cannot quite realise how these minute dust particles could have 
much effect in reflecting long Hertzian waves; and in the second 
place I do not think there would be much difference in the atmosphere 
over the downs between Dover and Deal, and that over the water im¬ 
mediately adjoining. One little illustration perhaps may tend to ex¬ 
plain how the difference may arise. If you look at the sun or the 
moon when rather low on the horizon, then when either is shining over 
intervening land, you see a general illumination and nothing more, 
but when shining over water you get blinding rays of light reflected 
from the surface, and it seems very plausible to assume that those 
Hertzian waves which impinge on the land are either absorbed or may 
be reflected right away into space, whereas on the relatively smooth 
surface of the water they are reflected on to the vertical conductors 
(applause), 
