Thirty-four of the crew of the _Roland_ had died since leaving the southern regions, and if Kerguelen had remained another week in these latitudes, he would have lost a hundred men! On his return to France, Kerguelen met with nothing but ill-will and calumny, in return for so much fatigue, so bravely born. The feeling against him was so strong that one of his officers was not ashamed to publish a memoir, in which all the facts were dressed up in the most unfavourable shape, and the failure of the enterprise thrown upon Kerguelen. We do not assert that he was entirely free from blame, but we consider the verdict of the council of war which deprived him of his rank, and condemned him to detention in the Chateau of Saumur, most unjust. No doubt the judgment was found to be excessive, and the government discerned more malice than justice in it, for a few months later Kerguelen was restored to liberty. The gravest charge against him was that of having abandoned his sloop and a portion of his crew, in the southern seas, who, but for the opportune arrival of the _Fortune_, must have perished. Probably, however, even this was much exaggerated, for a letter exists from the abandoned officer, M. de Rosily (afterwards vice-admiral), in which he begs to serve again under Kerguelen. The account of these expeditions is an extract from the apology published by Kerguelen during his imprisonment, a work which was confiscated by government, and on that account is extremely rare. We must now turn our attention to the account of expeditions which, although they did not result in discoveries, had an importance of their own. They contributed to the rectification of charts, to the progress of navigation and geography, but, above all, they solved a long-standing problem, the determination of longitude at sea. To decide upon the position of a locality it is first necessary to obtain its latitude, that is to say, its distance N. or S. from the equator, and its longitude, or in other words its distance E. or W. from some known meridian. At this period, no instrument for determining the position of a ship existed but the rope known as a log, which, thrown into the sea, measured the distance which the ship made every half minute; the proportionate speed of the vessel per hour was deduced from it. But the log is far from immoveable, and the speed of a vessel is not always the same, hence arose two important sources of error. The direction of the route was determined by the mariner's needle or compass. But every one knows that the compass is subject to variations, and that the vessel does not invariably follow the course it indicates, and it is no easy matter to determine the exact difference. These inconveniences once admitted, the question was to find a method exempt from them.