26 Illumination of Beacons and Buoys. [January, 
apparatus would certainly warrant the endeavour to bring 
this source of illumination into pra¢tice. The greatest 
obstacle to the adaptation is in the case of floating buoys, 
where the cable would be subject to abrasion against the 
sea bottom, in situations where the light would be most 
useful, always of the worst kind. Yet the wear could be 
brought, as we know from experience with telegraph cables, 
within such limits as would be practically reparable. 
Recent experiments with Wilde’s magneto-ele¢tric machine 
without carbons have been made with much better results. 
From various trials Mr. Stevenson has also found that the 
most brilliant light is Geta when bismuth points are 
employed. 
The remaining source of illumination is that by gas. In 
1853, Admiral Sheringham illuminated a buoy in this 
manner off Portsmouth. The gas was conveyed as far as 
possible in iron pipes, the condué¢tion being continued 
through a gutta-percha tube to the beacon. The gas was 
lighted by means of a platinum wire rendered incandescent 
by the passage of a voltaic current from a small battery on 
shore. The results, however, were not published till quite 
lately. 
A beacon on the Clyde, near Port Glasgow, was, in 1861, 
lighted with gas, and has since been maintained. This 
beacon is 300 feet from shore, and the supply of gas is 
regulated in a very ingenious manner. A float is so 
arranged in the principal burner that a certain pressure is 
requisite to admit of the passage of the gas, consequently, 
when the gas is shut off from the main each morning, the 
light would be completely extinguished were it not for a 
small burner that, being fed from a gas-holder of about ten 
cubic feet capacity, situate in the body of the buoy, remains 
alight all day. Again, each night as the pressure increases, 
the float closing the supply-tube to the principal burner 
rises, and the beacon is fully illuminated. The objection to 
this system, however, is the liability of the flame to extinc- 
tion—a risk from which the ele¢tric spark is free. The 
accumulation of water in the pipes is another serious 
obstacle; while in the case of ele¢tricity the risks of faulty 
insulation would be compensated by the use of duplicate 
wires. 
These numerous experiments, however, go far to prove 
that the illumination of buoys and beacons from the shore is 
perfectly feasible, and the time is not perhaps very distant, 
when, following the suggestion of Messrs. Stevenson, the 
entrance to the Port of Liverpool, for example, will be lit up 
