22 
THE TELEGRAPH 
and can be carried by one soldier. It has the advantage of 
being available between the advanced guard and the main 
body of an army, and in Afghanistan and Zululand it super¬ 
seded the flag signal commonly used in the English army 
between detached bodies of troops. It has everywhere been 
used where the electric telegraph could not be employed, and 
although it has occasionally failed from the want of sunshine, 
yet, for short distances, it has been found serviceable even 
under a cloudy sky. 
Sir W. Thompson has lately examined for the Ship-Masters’ 
Society, the various kinds of luminous signals now in use for 
distinguishing lighthouses. 
In his opinion, neither revolving lights of definite periods, 
nor lights with flashes at intervals of three or four minutes, 
are sufficient to ensure the safety of mariners, and the same is 
the case with coloured lights. 
Sir W. Thompson proposes to overcome the difficulty by a 
system of eclipses produced by revolving screens, which shall 
produce intermittent extinctions. The system is to be founded 
on the Morse alphabet, and each lighthouse is to be repre¬ 
sented by a letter. In support of his proposition, the eminent 
physicist has referred to the good results obtained with this 
system for the last three years at the Hollywood Bank Light¬ 
house, near Belfast, where the signals consist of two short 
eclipses followed by a long one. These are produced by means 
of a copper ring carrying a series of screens, which is turned 
by wheelwork. 
This appears to be an excellent system ; for a lighthouse 
sending out intermittent signals forming the first letter or 
the first two letters of its name according to the Morse code, 
would be immediately recognised by every mariner knowing 
in what seas he is sailing ; and in this way an international 
code of signals might be formed of the highest utility for safe 
navigation. 
The system is, in fact, one which cannot fail to be speedily 
adopted ; the more so as it can be adapted to existing light¬ 
houses without any difficulty, and at a trifling expense. 
The same thing will doubtless be done for shipping. All 
ships having steam power will certainly before long be fitted 
with the electric light, and the use of intermittent signals in 
