[_Face p. 80_ ] In the future, the types of roadless vehicles are likely to be great as the surface of the ground differs in various countries; also fuels of all kinds are likely to be burnt, such as petrol, oil and coal, and in tropical countries, where these fuels are scarce or expensive, producer gas is almost certain to become the main motive power. The most remarkable achievement as yet carried out by roadless vehicles is undoubtedly the crossing of the Sahara from Touggourt to Timbuctoo, during the winter of 1922–1923, by Citroën motorcars fitted with half tracks invented by Monsieur Kegresse. The distance travelled was three thousand six hundred kilometres, and the time taken was twenty days, that is on an average one hundred and twelve miles a day. All machines returned safely, and the total journey there and back was over seven thousand kilometres. The nature of the country crossed was by no means uniform, for it was sandy, rocky, mountainous and, in the neighbourhood of the river Niger, covered with tropical vegetation. To build a railway from Touggourt to Timbuctoo would cost, at the lowest reckoning, a thousand millions of francs—possibly much more; this alone accentuates the importance of the achievement and its interest to us, for the Empire contains thousands of square miles of roadless country. I fully realize that, though the roadless vehicle can replace the motor-car, it cannot replace the railway, if the railway is an efficient one. This is, however, not the problem. The problem is, first to bridge the gap between the producer and the railway, and secondly to create in undeveloped countries sufficient wealth to enable more railways to be built. Co-operation with existing railways, this is what must be aimed at. [Illustration: CROSSLEY-KEGRESSE CAR [_Face p. 82_ ] For purposes of illustration, I will take British East Africa as an example. A railway runs from Mombasa via Nairobi to the Great Lakes. Forty miles on each side of this railway, generally speaking, is commercially remunerative. This is the first belt I mentioned above, the second two belts are productively a gamble for any but capitalist pioneers, and the remainder of the country is but the playground of rich colonists who can afford to speculate on likely railway extensions in the future, or else of simple fools. I will now suppose that a reliable roadless vehicle exists which can transport across country five or ten tons of produce. What do we see? We see the first belt extending from forty miles on each side of the railway to a hundred miles, and the second two belts being pushed out, in vastly improved circumstances, fifty to a hundred miles on each side of the new central belt. In fact, we have more than doubled the central belt and trebled the belts adjoining it, and, in doing so, have more than doubled the commercial prosperity of the country.