On the 21st, at 11 a.m., while Lord Bridport, with the fleet, was standing across the Iroise passage on the larboard tack, with the wind from the north-east by east, the 74-gun ships Mars, Captain Alexander Hood, and Ramillies, Captain Henry Inman, which, with two or three frigates were on the look-out to windward, discovered and gave chase to two strange sail, distant about four leagues to the eastward. At 2 p.m., as the British advanced ships were getting abreast of the two strangers, then ascertained to be enemy's ships, a third, and a much larger sail, made her appearance about five leagues off, in the east-south-east, working up alongshore towards Brest. The latter became the preferable object of pursuit, and was therefore at 5 h. 45 m. p.m., chased under all sail by the Mars, Ramillies, and 38-gun frigate Jason, Captain Charles Stirling, the only three ships of Lord Bridport's fleet, that were near enough to obtain a sight of the stranger. At 6 h. 20 m. p.m. the Ramillies, carrying away her fore topmast, dropped astern ; and the chase was continued by the Mars and Jason, the body of the British fleet then bearing from the former west, distant 10 or 11 miles, and the Penmarcks east-south-east, distant about nine miles.

Every effort was used to accelerate the sailing of the Mars ; and she evidently gained, as well upon the Jason, as upon the enemy, now plainly seen to be a ship of the line. At 7 h. 30 m. p.m., the Penmarcks bearing south-east half-east distant seven or eight miles, the stranger evinced an intention to escape through the passage du Raz. Soon afterwards the Mars put about on the starboard tack ; and at 8 h. 30 m. p.m., Bec du Raz bearing north by east two or three miles, the French 74-gun ship Hercule, Captain Louis l'H�ritier, finding herself unable to work up against a strong current, dropped anchor and furled her sails. This was just at the mouth of the passage, and at a distance from Brest, the port she was endeavouring to reach, of about seven leagues. The Hercule then, carried a spring out abaft, and put herself in the best possible state to give a warm reception to the Mars, now fast coming up.

At 8 h. 45 m. p.m. the latter, who had by this time run the Jason nearly out of sight, hauled up her courses. At 9 h. 15 m. p.m. the Hercule opened her starboard broadside upon the Mars, and received an almost immediate return. Finding, however, that the strength of the current would not allow him, while under way, to take up a proper fighting position, Captain Hood resolved to anchor. Accordingly, at 9 h. 25 m. p.m., the Mars ranged ahead of the Hercule, and, having passed on to a short distance, let go her anchor. As the Mars dropped astern, the anchor on her larboard bow caught the anchor on the starboard bow of the Hercule; and, thus entangled, with their sides rubbing together, did the two ships engage, until 10 h. 30 m. p.m.; at which time the Hercule having failed in two attempts to board, and being dreadfully shattered in her hull, particularly on the starboard side, hailed that she struck.

So close had the ships fought, that the guns on the lower deck of each could not, as usual, be run out, but were obliged to be fired within board. With the exception of the jib-boom of the Mars, neither ship lost a spar. During the first ten minutes of the action, however, while the latter was obstructed in her man�uvres by the wind and tide, her bowsprit, foremast and foreyard received several of the Hercule's shot. In other respects, the damage to both ships was confined to the hulls. The Mars had her hammocks, boats, and spars shot through, and three or four of her first-deck ports unhinged in the collision of the ships : her hull also, was hit in several places. The Hercule's starboard side was riddled from end to end. Several of the ports were unhinged ; and, in some instances, the spaces between the ports entirely laid open. The contrast between the two sides of the ship was, indeed, most remarkable : the larboard side, which had been very slightly injured, was of a bright yellow ; while the starboard side, or what remained of it, was burnt as black as a cinder. The five aftermost starboard lowerdeck guns of the Hercule were dismounted, and several of the others much damaged.

The loss sustained by the Mars, in this long and close fought action, was necessarily severe. Out of a crew of 634 men and boys, she had her commander, captain of marines (Joseph White) one midshipman (James Blythe), 15 seamen, and four private marines killed, three seamen and five private marines missing (but in what way neither the official letter, nor the log, gives any account), and her third and fifth lieutenants (George Argles, badly, but who would not quit the deck, and George Arnold Ford), one midshipman (Thomas Southey), 36 seamen, two sergeants of marines, and one drummer wounded ; total, 30 killed and missing, and 60 wounded.

No accurate account has been given of the loss on board the French ship ; whose crew, as deposed to by her principal surviving officers, consisted of 680, being 20 short of her established number according to the latest regulation, and which would probably have been filled up on her arrival at Brest. Some accounts reckoned the killed and wounded of the French ship at 400 ; but the Hercule's officers, who were the best judges, did not consider the number to exceed 290, an amount greater, as it was, than two-fifths of her complement.