British free traders of the mid-nineteenth century brought the merchant's ledger to the aid of diplomacy when they claimed that the promotion of unrestricted oonnerc1al intercourse between nations was inseparable from that of universal peace. The application of this assumption in the conduct of British foreign policy between 1859 and. 1871 forms the subject of this study. It is based upon five commercial treaties which Britain concluded with various European countries and of which the well-known Cobclen treaty was the first. Although these brought about a state of virtual free trade among the leading trading countries of western Europe, they were, strictly speaking, contrary to Britain's policy of free trade adopted in 1846. Therefore, after a brief account of the free trade movement and of the free traders' blueprint for foreign policy, the circumstances which led. Britain to modify her post-1846 policy and. conclude the Cobden treaty are discussed in the early part of the study. With the conclusion of that treaty, the foreign Office and the Board of Trade entered a period of intense commercial activity during which they signed four more treaties. Their efforts were not entirely successful and the feeling that they were ill-equipped. for their commercial functions led to a parliamentary inquiry and the subsequent establishment of a commercial]. division within the Foreign Office in 1865. The era of free trade occasioned by the treaties was short-lived; by the 1870a most European countries had reverted to protectionism and the circumstances of this reaction axe considered in the seventh chapter. The idealism enshrined by the treaties stands in sharp contrast to the Bonapartist and. Bismarokian realism of the same decade; the grounds of this contrast and. the influence of the treaties on British foreign policy are discussed in the conclusion.