The Paris Metropolitan Railway, like its London namesake, is the most popular transportation agency in the city it serves. In a single year the French “Metro.” conveys as many as 792 million passengers, and, in one day, it has actually handled 2,366,000 travellers. This compares with the 310 million passengers handled annually by the London Underground, and the 229 million figure of the Berlin underground lines. The Paris Metropolitan Railway is at present a comparatively small system hedged in within the city walls. To meet the needs of growing business, an additional twenty-five miles of underground track within the city walls are now being constructed, while later it is intended to extend the tracks into the outlying suburbs and residential areas beyond the city proper. The total length of the “Metro.” is 95 kilometres. Some 174 stations are scattered throughout the system, thirty-seven of these being exchange points. During the peak hours no fewer than 279 trains'run simultaneously, with an interval of only 1 3/4 minutes between trains. Included in the improvement works now in hand is the provision of a good deal of new equipment such as lifts and escalators, or moving stairways, for the convenience of travellers. In carrying, by far, the densest traffic of any European railway system, the Paris Metropolitan Railway stands out as one of the most important of transportation undertakings.