Engineering Wonders of the World
Volume I

THE AFRICAN TRANSCONTINENTAL TELEGRAPH. 199 that specially tall poles had to be employed in order that the wire should not impede naviga- tion at any state of the water. These poles are made of wrought iron, and are 60 feet in height. The river-banks at the point selected for the crossing of the line are respectively 34 and 38 feet high, so that the brackets on the poles to which, the wire is attached are over 90 feet above the level of the water. The weight of the wire of this huge span, which is some 2,178 feet across, causes it to “ sag ” so much that in the centre it drops to within 54 feet of the river at low and 37 feet at high water level. The weight of this span of wire, it may be added, is 940 lbs. Poles similar to those employed, on the Zambesi were em- ployed for the passage of the Shiré River, though the span here is not so great. The poles usually em- ployed along the line are graceful tapering ones of wrought iron, twenty feet high, with flanged bases, A SIXTY-FOOT POLE BEING ERECTED ON THE BANK OF THE UPPER SHIRÉ RIVER. and, to facilitate transport, are made in two The Telegraph Poles. portions, easily fitted together at the site of erection. As a general rule they are placed about 100 yards apart, eighteen poles to every mile of country. For the most part the whole of the material for the con- struction of the line, as well as for the erection and equipment of the telegraphic stations, has had to be brought overland for long distances either by native carriers or by bullock-wagon, where the country was sufficiently open and level to permit of these methods of transport being used. The carriers displayed great powers Atti- tude of the Natives. of endurance. Their maximum load, 50 lbs. per man, they carried for days together without showing signs of fatigue. In certain parts of the line, however, it was possible to make use of the railway from. Beira to Salisbury, and of the Zambesi and Shiré Rivers, on which, the material and equipment were brought up in steamboats and dhows ; but for the greater part of the line recourse had to be had to native carriers. The building of such, a line through what was practically a virgin country must of neces- sity have had its exciting moments. Some of the tribes through whose coun- try the line was carried were at times disposed to be very hostile, and it needed con- siderable tact, and at the same time firmness, on the part of the small construction parties to prevent a collision. Such, tribes, however, were the exception rather than the rule. For the most part the innate curiosity of the natives overcame their fear or resentment at the white men’s presence in their midst. At times they would cluster round in great eager- ness to witness the work of erecting the poles and stretching the wire from one to the other. They had not the slightest idea what all the fuss was about, but were firmly convinced that there was “ magic ” in it somewhere. Under no circumstances could these natives be induced to touch one of the poles or a piece of the wire, or to approach the spot where the testing-instruments were at work. The workmen’s tools, however, attracted their cupidity—there is no greater thief in the world than the Central African native—and these they would purloin whenever they saw an opportunity. A very ingenious and uniformly successful ex- pedient, however, was adopted for keeping them at a respectful distance. This was the sudden discharge of an electric spark from one of the instruments, which never failed to send Method of Preventing Injury to the Line.