Thus the “grouping” which is permitted, and indeed actually carried out, by the German authorities, exceeds in degree anything of the kind known on the railways in this country. In France also, “grouping” of ports is sanctioned with a view to promote competition. The special import and export rates from Dunkirk, Calais, and Boulogne to Paris, which are equal in amount, notwithstanding the differences in distance, may be taken as an example:-- Dunkirk to Paris, 304 Kilometres. Calais ” ” 296 ” Boulogne ” ” 252 ” SECTION VII. DIFFERENTIAL RATES ON THE CONTINENT. In France, Belgium, and Germany, there are fewer ports competing with railways or with each other than in Great Britain. In each of those countries the principle of mileage rates has been nominally, and, to a large extent, in practice adopted. But in all of them causes similar to those which have here created so-called differential rates have been in operation. In each of them the fact of competition by water is recognised as a reason for charging reduced or special rates; such rates for export or import traffic exist, although the special rates for the latter traffic are fewer than for the former; and there are also special transit rates[22]. All these rates have been established after much consideration. Writing of the discussion of the subject in the Corps Legislatif in 1863, M. Aucoc observes in his well-known work, “Since that solemn discussion, the principle of differential tariffs has been placed beyond question.” He adds: “It may be well to mention also that, in the numerous judicial works on the working of railways, not only the legality, but the necessity and equity of conditional and differential rates have been almost unanimously recognised.”[23] [22] See _décret_ of April 26, 1862, quoted by M. A. de Foville in _La Transformation des moyens de Transport_ p. 68. [23] The following are some of the opinions of French statesmen and economists on the subject:--“_Dans ma conviction le tarif différentiel est à la fois juste, conforme aux vèritables intérêts économiques et nécessaires à la concurrence._” M. ROUHER. “_Les industries de transport par eau, par terre ou par chemin de fer ne vivent et ne prospèrent que par les tarifs différentiels. C’est en différenciant sagement leurs tarifs qu’elle attirent les marchandises et les voyageurs._” M. LEGRAND, _sous-secrétaire d’état au Ministère des travaux publics_: