from the point of departure of new route to the point of return. This gives an increased length of 6 miles 41 chains in the case of the Kayman Valley route over the Montague Pass route.

The general statement of the curves and straights is as follows:

5 chains radius, No. 62, of 404 chains aggregate.

The total length of line is scaled from the general plan of the gradient traverse, and this agreed fairly well with the distance by the traverse. Between Afgunst Neck and the crossing of the Zwart River the total scaled distance along the proposed centre-line of the railway was 100 feet longer than the traverse distance, although at one point it was 1,450 feet short; but the distance was again made up by additional windings into ravines over the traverse line. On the total distance to George the length found for the proposed centre-line of the railway was 1,685 feet short when compared with the distance by the gradient traverse.

The total length of 1 in 60 gradient is 15 miles 43 chains, all on the southern slope of the mountains. At the crossing of the Zwart River there is a level of 30 chains, and at the summit a level of 2 chains. Between the crossing of the Zwart River and the summit short lengths of 1 in 70 were introduced at points of severe curvature, and only in places where 5-chain curves were more than 10 chains long, the aggregate of such lengths of 1 in 70 gradients being 20 chains. From the summit to the junction with the Government survey on the Northern slope the distance is 3 miles 10 chains, all on a gradient of 1 in 70.

The structures required consist of one viaduct and one bridge. About 1 mile south of the summit a gorge in the mountain was crossed by the gradient traverse. A special section was taken at this place which proved that a viaduct of cantilever type would be required with a central span of 300 feet, and two side spans of 200 feet, with piers 120 feet and 90 feet high respectively, the height at the centre above the stream being 250 feet. A traverse was run into this gorge which proved the impracticability of curving into it. The crossing of the Zwart River is a work of much less importance. An accurate section was taken which

proved that a bridge would be required consisting of one central span of 90 feet and two side spans of 50 feet, with piers 60 feet high. Both these structures were on the straight, and drawings were prepared for them.

In addition to that at the summit there are four tunnels, three of which are shown in the Figs. These were necessary owing to the peculiarly cramped formation of the mountain, and without them it would not be possible to fit the line to the mountain side, even with so sharp a limiting curvature as 5 chains radius. The aggregate of these tunnels is 1,320 feet, made up as follows:Summit tunnel, 720 yards; tunnel at "Charlie's Neck," 150 yards; two tunnels in Kayman Valley, 180 yards and 100 yards respectively; and one 170 yards in the Zwart River Valley, the limiting depth of cutting for tunnel being 50 feet.

From the diagram plan showing the side slopes a trial section was compiled, and from the whole a fairly accurate estimate of the cost was obtained. The estimated cost was increased over the Montague Pass route in proportion to the increased mileage, the general class of work in each case being the same.

The Author carried out the first 9 miles, aided by three men, going into camp early in January, 1897; but at the end of April he was joined by Mr. Ragnar Filén, formerly of the Swedish Government Railways, who rendered him valuable assistance both in the field and in the office. All field and office work was completed by September. The wet weather and mists on the mountain much impeded operations, and the dense bush had to be burnt out before anything could be done. This survey necessitated nine different encampments on the mountain, three of which were not even accessible by bridle-path. With the exception of the first and the last, the camps were moved with the aid of carriers.

The Paper is accompanied by three drawings, from which the Figures in the text have been prepared.

(Translated and abstracted by GILBERT RICHARD REDGRAVE,
Assoc. Inst. C.E.)

THOUGH no official connection exists between Belgium and the Congo Free State, which is absolutely autonomous, there are so many intimate ties between the two countries that everything relating to the vast African territories, under the personal sovereignty of King Leopold, cannot fail to possess a powerful interest for the Belgian people. The Author shows that almost the entire Congo basin is comprised within the limits of the Free State, and that the numerous and important tributaries of the Congo distinguish its watershed from that of almost every other great river. The chief confluents and branches discharge into the broad stretch, known as the Stanley Pool, above which the Congo and its tributaries are navigable for upwards of 11,000 miles. Below Stanley Pool, as far down as Matadi, the river ceases to be navigable, owing to the falls and rapids caused by a descent of about 1,000 feet in a distance of about 217 miles. From Matadi to the coast the river is practicable for vessels of large tonnage, and Matadi is, in fact, the destined port of the Congo basin. It was clear that from every point of view it was a matter of urgent necessity for the sake of the future development of the country to provide means of transport between the Upper Congo and the navigable estuary at Matadi, and thus to do away with the interruption to traffic caused by the impassable rapids. From various considerations it is shown that the construction of a railway afforded the only practicable solution of this difficulty, the canalization of the river being out of the question.

As soon as Mr. H. M. Stanley had opened up the country by his explorations in 1878, the idea of the railway had been mooted, and as early as 1885 a syndicate of English capitalists approached the

'The original article appeared in the Annales des Travaux Publics de Belgique, vol. iii. (2nd series), 1898, pp. 575-675.

Congo Free State with a view to a concession for the construction of a railway from the Lower Congo to Stanley Pool. Affairs were, however, at that time hardly sufficiently advanced for the realization of this project, but shortly afterwards a Belgian Company was formed, with the modest capital of £50,000 (originally £40,000), to prepare the way for a more complete study of the question. This company was definitely launched on the 9th February, 1887, as the "Congo Company for Commerce and Industry," and the first step taken was to despatch two expeditions, the one to seek out and to survey the best route for the proposed railway between Matadi and Leopoldville, and the other to report upon the commercial prospects in the future of the basin of the Upper Congo. The first of these expeditions, the survey party, was in charge of Captain Cambier, who had already, on two previous occasions, travelled in Africa, and the second party was entrusted to the leadership of Mr. Delcommune, who had for 12 years been engaged in commercial pursuits on the Upper Congo. Captain Thys was at the same time appointed to proceed to Africa and to take charge of the two enterprises as the chief representative of the Company.

Some previous proposals, namely, that of Stanley for a railway from Vivi to Isangila, following the north bank of the Congo, and a scheme for a similar line from opposite points south of the river are noticed. Both of these lines would have terminated at Isangila, where a stretch of the Congo is navigable for whale-boats, skilfully managed by native oarsmen, as far up as Manyanga. From this point, a second railway would have carried the traffic to Stanley Pool. There had been also a projected line from Matadi to Stanley Pool direct, without break. The two former schemes, though they would perhaps have been less costly in point of execution, were open to grave objections, owing to the necessity for several transhipments and the great difficulties in the navigation above Isangila. The Company decided, therefore, to attempt to construct a railway direct from Matadi to Stanley Pool. At the period of the inception of the scheme, the country between these two points was wholly unexplored, but for the two caravan routes, the one to the north of the Congo, and the other to the south. The latter seemed to offer the fewest difficulties for the construction of the railway, and the survey party, which started in 1887 and returned in 1889, adopted this route. The conditions laid down for the railway were as follows:-The gauge was to be 29 inches; the maximum gradients 45 feet per 1,000; minimum radius of curves 2 chains, while tunnels and all heavy works were to be as

far as possible avoided. In order to save time and to reduce the preliminary expenses, the engineers were only called upon to furnish an approximate scheme, showing the possibility of constructing the line and enabling them to estimate the probable outlay. The difficulties encountered were, with three exceptions, readily overcome; these were (1) the section skirting the torrential stream, the M'Poso; (2) scaling the heights of Palaballa, which rise precipitously directly after that river is passed; this proved the most knotty point of the scheme; (3) in attempting to reach the Pool by the most direct route, the surveyors entered the valley of the Lukunga, a tributary of the Congo, the opposite bank of which presented a cliff-wall which was absolutely impassable and which attained in places a height of upwards of 3,000 feet. It was, in fact, an invincible obstacle, which appeared for a time likely to destroy all their hopes of success, since this rock-wall was found to follow the whole course of the river to its junction with the Congo, and thus constituted the separation between the basin of the Lukunga and that of the Congo. The only alternative open to them was to ascend the course of the river Lukunga, without, however, much anticipation of finding an outlet, since the general direction of all the tributaries on the left bank of the Congo was such as to cause them to conclude that it would speedily lead them into Portuguese territory, which was near at hand. By a lucky circumstance it was found, after following up the valley for from 12 miles to 15 miles, that the stream, in lieu of trending due southward, made a sharp bend to the north-east, encircling the precipitous cliffs on the right bank, which are only terminated northwards by the Congo itself. The survey line was, therefore, taken up the valley, and only diverted later to strike off towards the Stanley Pool, which was reached after crossing the Inkissi, the most important river which had to be traversed, and passing over the Tampa Plateau, the highest ridge of the chain of mountains encircling the central Congo basin. By means of a map (Fig. 1) of the Congo State, the Author explains the original route proposed and certain modifications, which were introduced during the execution of the work, with a view of shortening the distance and reducing the cost. The length of the line, as originally surveyed, was 285 miles, but the ultimate length is 241 miles. Some of the principal elevations above datum are as follows:-Matadi, at the starting-point, 86.6 feet; ridge of Palaballa, 918.6 feet; ridge of Zolé, 1,574.8 feet; ridge of SonaGongo, 2,444 2 feet (summit-level of line); ridge of Tampa, 2,083.3 feet; Plain of Stanley Pool, 1,033 4 feet.