If the road will not suit the vehicle, the vehicle must be made to suit the road. Here again the difficulty is economically almost insuperable. Balloon tyres, the use of light trailers and of multi-wheel vehicles will partially overcome the difficulty; but rubber rapidly deteriorates in tropical countries, and though a vehicle, such as the Renault six twin-wheel car, has carried out some wonderful performances in the Sahara and elsewhere, the maintenance of twelve balloon tyres practically rules it out of court in most undeveloped countries. If the bullock wagon is restricted to certain areas, and if the lorry demands a road which is prohibitively expensive, the only remaining sources of transport which can feed the railway are the pack animal and the human porter. _The Pack Animal._ In examining this last system of transport, I will begin with the human pack-animal, the native porter. Not only is this means of carriage the most primitive of all, which renders it somewhat of an anachronism in the twentieth century, but it is extravagant in the extreme. Economically it is unsound, since the human pack-animal stands in the way of the development of his country. In the first place his productive work is lost, and in the second, the load carried is so small as to offer little encouragement to the producer. Last, and by no means least, unlike the railway, as the amount increases, so does the cost per ton mile increase with it. On a large scale the system is impossible, and the substitution of pack animals for porters is but little less uneconomical, except in mountainous countries and desert lands, and in the latter, it would seem that the reign of the camel is approaching its end, since in most places where a camel can go a car can follow. TWO-DIMENSIONAL MOVEMENT The above, I admit, is a very brief summary of an immense and complex subject, namely, the bridging of the gap which exists between the producer and the arterial railway, or the producer and his market, if it be a distant one. Ruling out pack and porter as being too uneconomical to be used on a large scale, we are left with the wagon, the lorry and the light railway. All these three means can cover great distances, but they do not solve the problem, because the solution does not only lie in power to traverse distance, but in ability to cover the largest area in the shortest time.