While the Porte was thus engaged in the endeavour to add to its domain at the expense of the Republic of Venice, it was incurring a very serious shrinkage of Empire in the Mediterranean, along the northern coast of Africa. Historians agree in assigning to the middle of the seventeenth century the virtual severance from Ottoman rule of the two Barbary States of Algiers and Tunis. It is not possible to fix a precise date in either case, for the process of amputation was slow and was spread over some years, and long after the Sultan had practically ceased to exercise any real power over these dependencies the semblance and form of suzerainty was maintained. The main cause for the loss of these provinces was the practice which had grown up, under the corrupt administration of the Porte, of selling the posts of governors of them to the highest bidders in money. In place of men of energy and of capacity, able to control the unruly elements of mutinous soldiers and disaffected Moors and Arabs, governors were appointed under a system of purchase who were quite incapable of performing the duties of their office, and who merely thought of filling their pockets and recouping themselves for their outlay. The practice then arose for the Janissaries and other Ottoman soldiers forming the garrisons of Algiers and Tunis to elect their own chiefs. The appointments of these men, Deys, as they were called, were for a time submitted to the Sultan for approval or veto, but later this form was discontinued, and the Deys elected by the soldiery became the real dominant authorities in these States, and eventually superseded in form, as well as in substance, the feeble pashas sent nominally as governors from Constantinople. Virtual independence was thus achieved. Both States provided themselves with fleets of powerful war vessels, which roamed over the Mediterranean and the Atlantic as far as the coasts of Ireland and Madeira, preying upon the commerce of all countries, irrespective of whether they were at war with the Porte or not. They were, in fact, pirates. The captured crews were employed as slaves in the bagnios of Algiers and Tunis. The best evidence of the actual, though not yet of the formal, independence of these Barbary States was that other Powers sent their fleets to attack and bombard them, and to destroy, if possible, their pirate craft, without declaring war against the suzerain power, the Porte. Thus, as early as 1617 a French fleet, under Admiral Beaulieu, made an attack on the Algerian fleet of forty vessels of from two hundred to four hundred tons, and destroyed many of them. In 1620 a British fleet, under Sir Richard Mansel, in retaliation for the capture of no less than four hundred British merchant ships in the previous five years, made a similar attack on Algiers, without, however, much result. In 1655, another British fleet, commanded by Admiral Blake, under orders from Protector Cromwell, bombarded Tunis, and destroyed a great part of its