Night Traffic on the Suez Canal.
One of the most interesting applications of the electric light yet made, is to the passage of the Suez canal at night time. This great waterway, which is so important to all European nations, and particularly to this country, ran the risk of being choked by the continued development of the traffic through it in the years 1882 to 1885. At the end of this period, however, the canal company determined to light the channel at night time, so that the passage could be made without danger, and hoped in this way to sensibly diminish the traffic on the canal during the day, and to render the state of affairs less annoying to shipowners, until the enlargements now in progress could be completed. The company accordingly installed a complete system of beacons along the banks of the canal, supplemented by luminous buoys burning Pintsch gas on the water, and in this way the channel was clearly marked out.
It was soon seen, however, that this alone would be insufficient to insure safety in night passages, and it was therefore decided that every vessel moving along the canal at night must itself be supplied with arrangements for working a set of electric lamps on board. Rules were accordingly drawn up which provide that these lamps shall be four in number, one of which is to be a powerful light at the bow, inside of a projector lamp capable of throwing the beam to a distance of not less than 4000 feet in front of the vessel. The other lights are placed one at the stern and one on each side of the boat. The first vessel to make the passage under these regulations was the P. and O. steamship Carthage in 1886, the transit lasting eighteen hours, but with the improvements recently effected this time has now been reduced to sixteen hours for large vessels.
The Mangin projector is that principally employed, both war vessels and vessels belonging to the great mail companies being fitted with this apparatus. Smaller companies usually employ a portable apparatus, which they find ready for hire on their entering the canal, ami which they unship again on reaching Port Said or Suez. These sets of apparatus include the projector, a dynamo and a motor, and certain firms make a specialty of the business of hiring them out. The great companies generally employs similar apparatus, but are themselves the owners of the plant.
Other projectors are used beside the Mangin, amongst which are some with spherical mirrors and also lenticular projectors. But whilst the Mangin projectors, sixteen inches in diameter, require, at the most, a lamp using but forty amperes of current to give enough light, a spherical projector, twenty-four inches in diameter requires a sixty-five ampere lamp to give the regulation light. Theoretically these latter would have four times the power of the sixteen-inch Mangin projector were it not for their inferior mirrors which are not aplanatic, but experience has shown that owing to this defect they are in practice much less powerful. Hence to get the same light as with a Mangin projector, it is necessary to make one of the spherical type much larger, which in turn requires a larger and heavier dynamo and motor, and. therefore, also a greater steam consumption, This is especially inconvenient when, as is usually the case, the apparatus is portable, and hence it is not surprising to learn that ninety-five per cent of the vessels passing through the canal at night during the years 1887, 1888 and 1889, with their own apparatus, have employed the Mangin projector in spite of its higher first cost.
The night traffic on the canal has increased very rapidly since it was started. Thus in 1887 there were in all 371 night transits made, but in 1889 this number had increased to 2454 out of a total of 3420. or upwards of seventy-one per cent of the vessels passing through the canal, and four-fifths of the total tonnage used the electric light to assist them. At the same time the average duration of the passage has been reduced upwards of forty per cent. Putting these facts into another shape it appears that the effect of the electric light as applied at Suez has been the same as if the canal had been increased from twenty-two metres, its present width at the bottom, to thirty-two metres, an operation which would cost at least £4,000,000.Engineering.