The Marquis de Constanvaux had the frigate _Aurora_ built at his own cost for this experiment. Le Roy, however, decided that a cruise, with constant stoppages, at Calais, Dunkirk, Rotterdam, Amsterdam and Boulogne, lasting only from the 25th of May to the 29th of August, was far too short, and he demanded a second trial. This time his watches were sent on board the frigate, the _Enjouee_, which, leaving Havre, put in at St. Pierre near Teneriffe, at Salee in Africa, at Cadiz, and finally, after a voyage of four months and a half, at Brest. The trial had been a serious one, the latitudes and the state of the sea having both changed constantly. If the watch had neither lost or gained, it won the prize, which was in fact assigned to Le Roy. The Academy, however, knew that many other scientific men had bestowed their attention upon the subject, and for various causes had been unable to exhibit. They therefore proposed the same subject for the competition of 1771, and in 1773 they doubled the prize. F. Berthould imagined that he had reached perfection, but his watch had still to be tested by the trial of a long sea voyage. The _Isis_, a frigate of eighteen guns, was equipped at Rochefort at the latter end of 1768, and placed under command of Chevalier d'Eveux de Fleurien, known later as Caret-de Fleurien. Fleurien, then a midshipman, was already, though only thirty years of age, a well known _savant_. We have already mentioned his name, and shall find further occasion to do so. At this juncture, fascinated by mechanics, Fleurien had assisted Berthould in his undertaking, but that his disinterestedness might be above suspicion, he selected several officers to assist him in observing the motions of the watch which was entrusted to him. Starting in November, 1768, the _Isis_ put in successively at Cadiz, the Canary Islands, Goree, the Cape Verde Islands, Martinique, St. Domingo, Terra Nuova, the Canaries, Cadiz again, and reached Aix Island on the 31st of October, 1769. The watches, carried through climates alternately cold, hot, and temperate, had experienced every vicissitude of climate, and at the same time had been exposed to all the variations of the sea, in the roughest season of the year. After this trial, which had redounded so much to his honour, Berthould obtained the rank and pension of an inspector of nautical watches. This expedition had other results which concern us more particularly. Fleurien took a number of astronomical observations, and hydrographical surveys, which resulted in a well-founded condemnation of the maps of his country. "For a long time," he says, in his account of his voyage, "I did not attempt criticism of the maps belonging to the Society; I wished to limit myself to giving new details by which they might be rectified; but I found such numberless and dangerous mistakes, that I should have considered myself culpable towards mariners if I had neglected fully to point them out."