The two inner lines of each set were devoted to long-distance, express traffic, and the two outer to intermediate transit, corresponding to the ordinary trains of the present day. Thus, for example, the train by which Olga and Serge were about to travel, stopped only at Brussels, Berlin, Königsberg, Moscow, Nijni Novgorod, Tomsk, Tobolsk, Irkutsk, and Pekin, which was reached by a line running through the Salenga valley and across the great desert of Shamoo, while from Irkutsk another branch of the line ran north-eastward viâ Yakutsk to the East Cape, where the Behring Bridge united the systems of the Old World and the New. The usual speed of the expresses was a hundred and fifty miles an hour, rising to two hundred on the long runs; and that of the ordinary trains, from a hundred to a hundred and fifty. Higher speeds could of course be attained on emergencies, but these had been found to be quite sufficient for all practical purposes. The cars were not unlike the Pullmans of the present day, save that they were wider and roomier, and were built not of wood and iron, but of aluminium and forged glass. Their interiors were, of course, absolutely impervious to wind and dust, even at the highest speed of the train, although a perfect system of ventilation kept their atmosphere perfectly fresh. The long-distance trains were fitted up exactly as moving hotels, and the traveller, from London to Pekin or Montreal, was not under the slightest necessity of leaving the train, unless he chose to do so, from end to end of the journey. One more advantage of railway travelling in the twenty-first century may be mentioned here. It was entirely free, both for passengers and baggage. Easy and rapid transit being considered an absolute necessity of a high state of civilisation, just as armies and navies had once been thought to be, every self-supporting person paid a small travelling tax, in return for which he or she was entitled to the freedom of all the lines in the area of the Federation. In addition to this tax, the municipality of every city or town through which the lines passed, set apart a portion of their rent-tax for the maintenance of the railways, in return for the advantages they derived from them. Under this reasonable condition of affairs, therefore, all that an intending traveller had to do was to signify the date of his departure and his destination to the superintendent of the nearest station, and send his heavier baggage on in advance by one of the trains devoted to the carriage of freight. A place was then allotted to him, and all he had to do was to go and take possession of it.