22. The rate of postage upon newspapers printed and published in Canada, and issued not less frequently than once a week, from a known office of publication, and sent to regular subscribers in Canada by mail, shall be as follows: upon each such newspaper, when issued once a week, the rate for each quarter of a year, commencing on the first of January, first of April, first of July, or first of October of each year, shall be five cents, when issued twice a week, ten cents, when issued three times a week, fifteen cents, when issued six times a week, thirty cents, and in that proportion, adding one rate of five cents for each issue more frequent than once a week; and such postage must be pre-paid in advance from the first day of the quarter from which the payment commences, for a term of not less than a quarter of a year: ... provided, nevertheless, that _Exchange Papers_, addressed by one editor or publisher of a newspaper to another editor or publisher, may be sent by Post free of charge. 23. On all newspapers sent by Post in Canada, except in the cases hereinbefore expressly provided for, there shall be payable a rate not exceeding two cents each, and when such newspapers are posted in Canada this rate shall in all cases be prepaid by postage stamp affixed to the same. 24. For the purposes of this Act, the word "Newspapers" shall be held to mean periodicals published not less frequently than once in each week, and containing notices of passing events. 25. The rate of postage upon periodical publications, other than newspapers, shall be one cent per four ounces, or half a cent per number, when such periodicals weigh less than one ounce and are posted singly, and when such periodical publications are posted in Canada, these rates shall in all cases be prepaid by postage stamps affixed to the same. 26. On books, pamphlets, occasional publications, printed circulars, prices current, handbills, book and newspaper manuscript, printer's proof sheets whether corrected or not, maps, prints, drawings, engravings, photographs when not on glass, in cases containing glass, sheet music whether printed or written, packages of seeds, cuttings, bulbous roots, scions or grafts, patterns or samples of merchandize or goods, the rate of postage shall be one cent per ounce; provided that no letter or other communication intended to serve the purpose of a letter be sent or enclosed therein, and that the same be sent in covers open at the ends or sides or otherwise so put up as to admit of inspection by the Officers of the Post Office to ensure compliance with this provision--and this postage rate shall be prepaid by postage stamps in all cases when such articles are posted in Canada.