A Section Along the Railway from Cape Town to the Victoria Falls Author(S): A
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A Section along the Railway from Cape Town to the Victoria Falls Author(s): A. H. Wallis Source: The Geographical Journal, Vol. 36, No. 3 (Sep., 1910), pp. 339-343 Published by: geographicalj Stable URL: http://www.jstor.org/stable/1777310 Accessed: 07-05-2016 01:33 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The Royal Geographical Society (with the Institute of British Geographers), Wiley are collaborating with JSTOR to digitize, preserve and extend access to The Geographical Journal This content downloaded from 143.89.105.150 on Sat, 07 May 2016 01:33:32 UTC All use subject to http://about.jstor.org/terms A SECTION ALONG THE RAILWAY TO VICTORIA FALLS 339 believe in the excavating powers of ice, and it is mainly " ambulando " that I have been led to a different solution of this hard-fought controversy. The PRESIDENT: The subject of our discussion to-night has been the effect of covering the surface of the ground with ice. The slow geological changes which take place in these circumstances must depend on a large number of factors -on the hardness of the rock; on the slope and direction of the valleys; and on various meteorological conditions; and the problems involved are therefore of extraordinary difficulty. It is not to be wondered at that many questions thus presented have not yet been solved. I am sure most of us who are not experts have felt quite convinced by Prof. Garwood's eloquent presentment of his case. It is, however, fair to remember that we are somewhat like the jury who has heard three or four able advocates on one side and nobody at all on the other. In any case, we all must hope this discussion will be continued until the parties involved in it arrive at a satisfactory conclusion on these difficult problems, - A SECTION ALONG THE RAILWAY FROM CAPE TOWN TO THE VICTORIA FALLS.* By A. H. WALLIS, F.R.G.S., Acting Resident Engineer, Cape Government Railways, Mafeking. IN submitting to the Royal Geographical Society a section along the railway, the writer is of opinion that this is the first complete section of the route that has ever been prepared along the southern part of the continent, and it is hoped that the data will prove of interest to geographers and geologists. In order to show exactly what value attaches to the information furnished, the following particulars are given :- The section is plotted to an exaggerated scale, the horizontal scale being 20 miles per inch, whilst the vertical scale is 500 feet to the inch. The vertical ordinates are plotted to each mile of railway, involving the plotting of 1640 vertical ordinates. The data are obtained from the official records of the Cape Government Railways and the Rhodesia Railways, Limited. The levels were taken with an ordinary " dumpy " level, from low-water level ordinary spring tide at Cape Town, with a permitted variation of 0'03 foot per mile. The permission of the Cape Government Railways and that of the Rhodesian Railways, Limited, have been duly obtained for the purpose of this paper. The section has been carefully plotted. Scaling from the vertical ordinates may be safely accepted as exact to within 10 feet. To those unacquainted with the effects of the exaggerated scale, a warning should be given not to conclude that the continent of Africa, south of the Zambezi, is serrated to the extent as shown on the section; for were the horizontal scale plotted to the same scale as the vertical, the section would of necessity be several hundred yards in length to ensure the surface levels being seen in their true position. The surface levels of the section give their true geocentric position, in as far as sea-level has been assumed as uniformly geocentric. The datum is shown on the section as a straight line. It should more properly be shown on the section as a curve forming an arc of the circumference of the Earth; but it has been shown rectilinearly merely for the purpose of convenience, and the numerical data giving the heights of the * Sectional Diagram, p. 380. This content downloaded from 143.89.105.150 on Sat, 07 May 2016 01:33:32 UTC All use subject to http://about.jstor.org/terms 340 A SECTION ALONG THE RAILWAY various places are given as above sea-level in every instance. The levels were taken, as stated before, with an ordinary dumpy level, no coefficient for correction of curvature being adopted. Since the observations taken do not extend over more than 5 chains in each direction from the instrument, resulting in an observation of 10 chain lengths of true level, in which observation the collimation line of each was naturally tangential to the surface of the Earth, it is clear that each series of observations automatically corrected itself for curvature, inasmuch as each additional collima- tion line was tangential to the curvature of the Earth. As stated before, a limit error of 0'03 foot per mile was allowed. This error is naturally non-cumulative, the errors of plus being assumed to cancel the errors of minus, as equal sights were taken at equal distances from the position of the instrument. It must be admitted, in response to a possible query, that these levels have not been " tied in " with sea-level at its northern point. The direction of the railway is shown on the accompanying map by a broad red line, and the figures given in red denote the mileage from Cape Town. The railway, being of necessity a pioneer line, does not run in a straight line from Cape Town to Victoria falls, between which points there is a distance approximately of 16 degrees of latitude, or 1112 geographical miles, but meanders to such an extent as to give the distance along the railway as 1640 statute miles. Again, it must not be concluded that between Cape Town and Beaufort West (339 miles) the section given is a true outline of the country, since naturally a railway has to develop for gradient, avoiding the highest points and crossing ranges of moun- tains on the lowest and most accessible positions. This will account for the absence on the plan of Table mountain, 3550 feet in altitude, the range of moun~ tains at the Paarl (36 miles), south of Worcester (85 miles), the Hex river mountains at 145 miles, and further ranges at 186 miles, 230 miles, and 270 miles, at which points probably there are peaks towering as high as nearly 7000 feet; but at the same time the section is of value, as it gives an idea of the wrinkling up of the Earth's surface in the manner referred to later in this paper. Geographers may be assured that from Frazerburg road (290 miles from Cape Town) the section is fairly typical of the country as far as Kimberley (647 miles), although in the stretch of country referred to there are mountains east and west of the railway, reaching a height of probably 5000 or 6000 feet. From Kimberley to the Victoria falls, the railway can be safely assumed as strictly typical of the surface of the country, it being a pioneer surface line in which banks and cuttings have been studiously avoided, thus making the railway section show a true section of the country. It may be here pointed out that the railway between Francistown (1234 miles) and Bulawayo (1360 miles) practically runs upon the watershed of the country. To commence with the section. It will be seen that Cape Town is the zero line of the railway, rail level of which is 10 feet above low-water ordinary spring tide. Cape Town is situated .at the foot, and on the northern side of Table mountain, whose altitude is generally considered at 3550 feet. From zero the railway rises steadily to 650 feet at a distance of 27 miles from Cape Town, after which it falls on its way past Paarl (35 miles) and Wellington (45 miles) to 200 feet above sea-level at 63 miles' distance from Cape Town. It then rises at 85 miles to about 850 feet above sea-level, dropping to 720 feet at 98 miles, where the Breede river is crossed. From Cape Town to 116 miles the railway altitude lies below 1000 feet, but after this point the Hex river mountain climb is com- menced, and by the time 145 miles' distance is reached the railway attains an altitude of 3160 feet. This content downloaded from 143.89.105.150 on Sat, 07 May 2016 01:33:32 UTC All use subject to http://about.jstor.org/terms FROM CAPE TOWN TO THE VICTORIA FALLS. 341 It may here be mentioned, to prevent repetition, that the mileages given in this paper are the distances throughout from Cape Town. From 145 miles to 160 miles the railway drops once more to 2530 feet into the valley of the Touws river, after which it rises again at Pietermeintjes to 3600 feet, an altitude which it does not attain again for 150 miles northwards. The line drops on its way past Matjesfontein to Laingsburg, where it crosses the Buffels river at 213i miles at an altitude of 2140 feet, rising to an altitude of 2720 feet at about 230 miles, from whence it again drops to the valley of the Blood river to 1650 feet at 253 miles, and a few miles further on, to 1560 feet, where it crosses the Dwyka river, rising again at 270 miles to 2300 feet, and falling again to 1760 feet at about 287 miles, where it runs along the valley of the Gamka river near Frazerburg road, from which point it steadily follows the Gamka river as far as Beaufort West (339 miles) to an altitude of- 2840 feet.