It was feared that if an administration derived no benefit from transit traffic it might be led to discourage it, to the detriment of general facilities for the transmission of mails, and the Congress arrived at the conclusion that some method of specially remunerating all countries for transit services ought to be devised. A simple reservation as regards special expenses caused by transit traffic was objected to on the ground that in most cases the international traffic was forwarded by the ordinary means and no special expense was caused--the real causes of Post Office expenses being the services of despatch and delivery.[584] Indeed, it was contended on this ground that the transit of international mails could not be regarded as a service rendered. Agreement was reached on most of the points raised by the proposals, and a Convention constituting an International Postal Union, under the title "L'Union générale des Postes,"[585] was signed on the 9th October 1874, to become operative on the 1st July 1875. The chief provisions of the Convention in regard to the rates of postage were as follows:-- (1) The rate of postage for the Union was fixed-- (_a_) At 25 centimes for single letters, with liberty for each country, as might be necessary on account of its monetary system or for other reasons, to fix a higher or lower rate, provided that such rate was not greater than 32 centimes, and not less than 20 centimes. The unit of weight for a single letter was fixed at 15 grammes, and the scale of progression was by steps of 15 grammes. (_b_) For postcards, half the rate for letters. (_c_) For printed matter, samples, and commercial papers the unit rate was fixed at 7 centimes, with liberty for each country to fix a rate not exceeding 11 centimes or less than 5 centimes. The unit weight was fixed at 50 grammes, and the progression of weight was by steps of 50 grammes. The maximum limit of weight for samples was fixed at 250 grammes, and for printed matter and commercial papers at 1,000 grammes.[586] (2) In cases where letters were forwarded by sea for distances over 300 miles, a surtax not exceeding half the general Union rate of prepaid postage might be added to the normal rate. (3) The proposal as to the division of postage was accepted, with slight amplification.