The Canadian tariff has been a singularly faithful mirror of economic and political change in this country, but it is a glass through which much has been seen darkly. This study is an attempt to improve the view. It traces the administration of the tariff through Canadian history, and provides the first complete treatment of the subject and its significance for the country's commerce. Dr. Blake's work begins with customs administration during the French regime, and follows with the British period---the struggle for responsible government, the problem of smuggling, and the establishment of free ports. The author discusses such early problems as customs union in the Canadas, reciprocity and the Galt tariff, and ad valorem duties and their administrative consequences. Confederation and its effect on customs administration are analysed, as are the tariff schedule up to modern times, valuation and the effects of war, and the system and problems of appraisement. The customs establishment since Confederation is studied under such heads as organization, problems of adjustment, and political patronage in the service. Finally, the Canadian Tariff Board is put under examination. This study does not constitute an argument on either side of the policy controversy as regards free trade or protection nor is it a linearly historical treatment of Canadian commercial policy. It is an attempt to fit into the Canadian environment certain more or less theoretical concepts which may serve to explain the tariff as an important economic institution. It will be of interest to students of Canadian economic history, particularly in the area of national revenue.