The postcard has proved immensely popular. Its use for formal and unconfidential communications is a great convenience. By avoiding the necessity for folding and enclosing in envelopes, time is saved in the making up of correspondence for the post; and the saving in postage when a quantity is sent out is very considerable. The cards are a convenience also in the practical working of the Post Office service. Their use diminishes both the weight and bulk of the mails; on account of their lightness and uniformity of size and shape large numbers can be packed together in small space. In this respect they contrast strongly with the irregularly shaped packets of books or of general merchandise, which represent the maximum of encumbrance to Post Office working. The introduction of the picture postcard gave a great impetus to the use of this means of correspondence. Except in France, the traffic has assumed large dimensions. In the United Kingdom in 1913-14 the total number of postcards was about 926,000,000, while the total number of packets passing at the letter rate was about 3,478,000,000.[525] (V) RATE FOR PRINTED MATTER FOR THE BLIND The low rate for matter printed in raised type for the use of the blind is a purely philanthropic concession.[526] In the United Kingdom the rates are:-- For a packet not exceeding 2 ounces in weight 1/2d. " exceeding 2 ounces and not exceeding 5 lb. 1d. " " 5 lb. " " 6 lb 2d. It will be noted that the initial penny rate is maintained (the 2 ounces for 1/2d. being merely the ordinary printed matter rate), but a comparison with the ordinary parcel post rates (see Chapter III) will show that if, as there is reason to believe, those rates are unremunerative, the rates for literature for the blind must involve a heavy loss on each packet. The number of packets is, however, only some 300,000 per annum. Similar low rates are in operation in other countries. In the United States packets containing matter of this kind are carried free. * * * * * (VI) MINOR RATES IN THE UNITED STATES AND CANADA